"Brus, however past participles might behave in Latin is irrelevant to English."

Surely you mean: "... how past participles might behave in Latin is irrelevant to English."

Yes, I know. But it proves they are adjectives, which was the essential thrust of my argument.

That they are stuck with being passive in Latin is indeed irrelevant to how they behave in English, certainly. But you cannot really get away in formal English with saying "I was sat" unless it is clear who sat you there. This is because "I was sitting" is the imperfect tense, and "I was sat" is the perfect tense and by the way passive voice. "I was seated" is a challenging one to define, of course. "I was seated at a window table by the waiter" sounds more polite, suggesting that you went along with this arrangement, than "I was sat in the corner by the teacher" which suggests she made you sit there to humiliate you. "I was seated in the corner by the teacher" suggests that she went out of her way to make this pleasing arrangement, because it was a nice place to sit.

I was sitting on a bar stool earlier today, avoiding (for obvious reasons of diplomacy of course) mentioning any of this to any of my interlocutors, some of whom at times employ this quaint form of dialect without making it at all clear that they had been sitting anywhere other than by their own choice, and indeed would not have taken kindly to any attempt to humiliate them by imposing bad seating arrangements.

Those who could not grab a stool were not left stood, but they were left standing.

Er, I said run and flown, no?

I like your argument, Warsaw Will. Here's a point to make: past participles passive ARE adjectives. In Latin they are all passive, and they are adjectives. You can tell because of their endings-system of declension, as well as by their meaning. Only deponent verbs have active-in-meaning past participles. You cannot say for example "having sent", oddly enough, as there is no deponent verb meaning "send", only "having-been-sent" (forgive the hyphens) but there is a deponent verb "go" so you can say, for example, "having gone". But it as clear as can be that they are adjectives, like the English examples discussed above. Ah! Latin! the key to the door of an understanding of so many things, not least language.

Sat and stood do indeed rank with ran and flown. The implication, grammatically, is passive, which is to say someone else did it to our subject, and the agent who performed the deed is told to us with a phrase introduced with "by". I was stood in the corner begs the question by whom?
So: I was stood in the corner by the teacher. I was sat at my desk by the invigilator. I was run out town by the sheriff. He will be flown secretly out of the country to South America.
It is common, in England, to hear "I was sat" meaning "I was sitting", but that is not to say it is correct. If this site is not about correct English what is it for?

DA Wood: Fanshawe is the pronunciation among the cognoscenti of "Featherstonehaugh", ridiculously but truthfully enough. Farnborough is where they have the air show.
I worked as a teacher with a fellow called Fanshawe. A colleague was overcome with mirth when she heard two kids looking at the timetable and saying "Oh no! We have double Fanny today". This was not helped by the fact that in England Fanny does not mean what it does in the US. (Here it is round the front, er, enough said).

I'm really sorry I said all that, but I am pressing submit anyway.

"Your teen is more at risk while on its restricted licence” is no good, is it? The teen in question is not genderless, but of unknown gender (presumably, or why not "his" or "her" licence?). If of unknown gender I use "his" as default. If someone objects that the teen may be a girl I say masculine is ordinary, feminine special, special is reserved for when it is definitely deserved, and I suggest that for those who think otherwise the way to do it is "Your teen is more at risk while on his or her restricted licence". French uses 'ils' for 'they' unless the group is exclusively, and known to be, feminine, and I take my stance with an eye on that grammatical example, as well as the fact that it has been correct standard English for a very long time, the alternative 'they' being sloppy.
I don't think we should use literary superstars are our model for correct grammar - that is not what they become superstars for, rather for characterisation (Jane Austen), description, linguistic supremacy (PG Wodehouse), creation of atmosphere, plot etc. I am sure that planning to follow adherence to strictly grammatically correct English is not their game. I do think it should be so of journalists, however, and in most cases it is so.

DA Wood: "Well, let's endeavor to stamp out as many (exceptions) as we can, just like elephants do with their feet." Actually elephants are very careful not to do any such thing. They are terrified of mice, in case they trample on them. Or maybe it is just an aesthetic thing, finding squashed mice distasteful. We must be the same about exceptions, I suggest.

goooofy says that there is a "long-standing custom" to use "they" as a common-gender, common-number pronoun. It's been used for 700 years with antecedents like "everybody" (discussed above) , "who" (which is plural when referring to a plural antecedent, as in 'people who', and nouns that can apply to either gender, he says, and quotes Shakespeare, who is not exactly well known for his adherence to the grammatical rules of English.

"There's not a man I meet but doth salute me
As if I were their well-acquainted friend"

I would have everybody marry if they can do it properly - Austen, Mansfield Park, 1814

...every fool can do as they're bid - Jonathan Swift, Polite Conversations

A person can't help their birth - Thackeray, Vanity Fair

Now, I am reminded of the priest/minister/clergyman/vicar who each Sunday lectures his congregation on the evils of alcoholic drink, until one Sunday, wearying of this annoying crusade, an ancient member of his congregation calls out "did not the good Lord turn the water into wine at the wedding at Cena?" and was met with the instant retort from the pulpit "Aye, he did, and we don't think any the better of him for it". I feel much the same about the 'authorities' quoted by gooofy above.

It is all part of the slippery slope. As the man says, the horrors such as the football, son, father example seems "newer and not yet standard". Not yet! When it is, I shall emigrate to France, where they have a committee to prevent such atrocities against their own language, and the wine is cheaper.

Jasper's remarks:

'Popular? One day ..?' Is that not what I am railing against? That is exactly what I say we don't want! What is genderless about a person? A person is male or female, masculine or feminine, and there is nothing genderless about that.

'More convenient?' = lazy. "One day may become acceptable ..." means that day has not yet come, and I say, put off that day until nothing matters any more anyway, when there is no further need for discussion of standards in English and we all just give up!

It isn't acceptable yet, and long may things stay that way. Prescriptivist? What? My dictionary says that means "sanctioned by long-standing custom" and "giving direction, rules, or injunctions". Oh yes, that sounds good to me. What else would you want on a site like this?

"Did everybody leave early because he wasn't enjoying himself?" Oh no: "Did everybody leave early because they weren't enjoying themselves?". 'Everybody' is a plural concept surely? How could it conceivably be singular = one person = everybody?? In itself the word means something like "each and every individual" which is singular, but the idea behind it: I do not think so!
That example given would indeed be pure pedantry; I am grumbling about statements, in considered, published prose as in newspapers, such as " The father told his son to take their football into the garden". Whose football, hey?

Excellent news, Chloe. As I said before, I think, the first time I heard this expression, thirty years ago or so, it was teachers saying it to their pupils whose own parents would not use this quaint form. I thought perhaps they told their pupils to "stay sat" because they had indeed been made to sit, and they were trying to make a subtly point. As you say it is now heard everywhere, creeping even into the speech of politicians anxious to seem 'of the people' and who therefore prefer demotic to correct forms. I am appalled to hear it used by BBC reporters and journalists who, I gather, have been told to talk this way - there was an article by Joan Bakewell in the paper the other day in which she regretted the grammar and elocution lessons she had received in her youth, as she is now given fewer commissions because she sounds "too posh"!

You say it should be "It's you who is wrong" but I disagree: I would say "It is you who are wrong", and this is why:

You say the word "who" refers to the subject "you", but inherits only the number (singular or plural) of the subject. "You" here is the antecedent, which is then represented by "who". So "is" depends on "who" = "you", so 'you ... who ... are ...'.

You say that 'in this sense you can consider the phrase "who is wrong" as a (complex?) clause'. It is a clause, yes (not a phrase, which would not include a verb; this clause does) and there is nothing complex about it; it is a relative clause in which the relative pronoun 'who' relates/refers (from the Latin 'refero, referre, retuli, relatum' = to carry back) to its antecedent ("lying before") 'you'.

So therefore: I ... who ... am, you ... who ... are, he/she ... who ...is, we ... who ... are, and so on.

So when you say ' you wouldn't say "It's I who am wrong." ', I say I would, for it is correct. This time it is you who are wrong, I am afraid.