John has pegged the issue pretty well, and Merriam-Webster's Dictionary of English Usage agrees. Their conclusion, which they quote from another source, is this:

"Many people use "lay" for "lie," but certain others will judge you uncultured if you do. Decide for yourself what is best for you."

The intransitive use of "lay" was on the decline at the same time that grammarians were ascendant. Since only the educated studied grammar, lay v. lie became a marker beyond importance.

This is not to say that conventional standards of usage are irrelevant. Here I agree with Marilyn. Understanding standard usage and its rules is vital. But grammatical rules are not commandments. Ordinary speech, or writing, should usually follow precept. Once understood, rules may be tested, even flouted, if to the advantage of meaning.

Really Marilyn? That old canard? I'm loath to cock a snook at even so learned a maven as you, but "lay versus lie" is not so much a grammatical issue as a social one.

I presume you are alluding to the widespread taboo on using "lay" intransitively for "lie." The simple rule is generally this: "lie" is for people, "lay" is for things. (Easy to remember: many people lie.) But whence the distinction? I'll tell you whence: from long dead grammar cops with a social agenda. You de-bag the cat yourself when you quotationize "educated." For "lay" and "lie" have long been in the same bed.

Evidence, you say? OK. From Merriam-Webster's Dictionary of English Usage:

"The OED shows that "lay" has been used intransitively in the sense of "lie" since around the year 1300."

Which should, but won't, lay the issue to rest. There is more. M-W also says:

"The conflict between oral use and school instruction has resulted in the distinction becoming a social shibboleth – a marker of class and education."

I know what you're thinking: educated people talk good. Ergo people lie and things lay. But "educated" people didn't create English, or any language, except Esperanto. And when did anyone last converse in that flat tongue? No, language is created, nurtured and cultivated by poor slobs who wouldn't know an intransitive verb if it gave them a bus transfer, bless 'em.

And yes, I know exactly how snobbish that sounds.

It is unsurprising that "conversate" is found in online dictionaries. In my experience, most online dictionaries, Merriam-Webster's included, are descriptive rather than prescriptive. (In fact, most modern paper dictionaries are descriptive. Some say it started when Webster's Third included the word "ain't," loosing the hounds of criticism from the prescriptive crowd.) Some dictionaries include caveats for disputed words like "ain't" or "irregardless." In the case of "conversate," Merriam-Webster Online simply calls it a "back-formation from 'conversation' " without further comment.

Merriam-Webster Online dates "conversate" to 1973. This doesn't mean that it originated then, that's merely the earliest written example they could find of it. It likely was in spoken use before that; it may be regional or dialectical, or even slang. Merriam-Webster's Dictionary of English Usage has no entry for it, which suggests that it is not common. I have never heard or read it.

My own opinion is that "conversate" is unneeded, since we already have "converse," and I wouldn't use it. Many consider it improper, and they have a strong case; it is at best nonstandard. But I also wouldn't get upset with those who do. If you don't like it, don't use it. Just don't make a fuss about it. Unlike, say, cancer, words may wither away if they are ignored, and unused. Who can say where "irregardless" would be if it hadn't made every words-I-hate-most list for the past seventy years?

Sarcasm? Yeah, there's an app for that.

"Good night, Mrs. Calabash, wherever you are" was Jimmy Durante's radio sign-off.

This has been mad fun. John and Marilyn have engaged in the kind of meandering yet purposeful debate that makes this site worth reading, even if – or perhaps because – they have strayed so far from the original question that I can scarcely recall it. And all of this with civility and erudition. Kudos. And carry on.

"Get" has a bad reputation. Yet it's got solid provenance: by Middle English out of Old Norse. "Get" has been around for so long that it's acquired multitudinous meanings. It's a strong word, sharp and guttural, which, I suspect, is why it's suspect.

So what's wrong with "get," which Merriam-Webster's "Dictionary of English Usage" calls "one of the more important verbs in English"? They say it's because "get" is perceived to be "vigorous." That may be true. "Get" might be a four-letter word if it weren't a three-letter one. And there are almost always gentler words available. "Choice English" prefers gentler words, even to the point of blandness.

Get with it. Get it done. Get going. Get Carter. Get the point? There is nothing wrong with get, got or gotten. Got it?

I did a little poking about on the internet. It turns out that Grammar Girl listed "went missing" as her pet peeve for 2008:

"...if any reporters are listening, here's the deal: "Went [sic] missing" actually isn't wrong, but it annoys a lot of Americans, so you might want to say "missing" or "disappeared" every once in a while."

For the record, peevish people should get real pets; it might relax them. But G. G. does note that "Went missing actually isn't wrong." That's because, as she herself notes. "go is quite a versatile verb." It generally implies movement, but a person may "go crazy" without actually traveling. Much.

Grammar Girl attributes the invasion of America by "went missing" to the press, and she's probably right. But if a a midwestern sheriff is using it, it's here to stay.

There is ample antipathy on both sides of the Ocean Sea to usages perceived to be "theirs." This is not new. Fitzedward Hall (now there's a name!) in "Modern English" (1873) cites "The London Review" (1864) as saying:

"The nineteenth century has witnessed the introduction of abundant Gallicisms, Germanisms, Americanisms, colonialisms, and provincialisms; nearly all needless, or easily to be supplied by more correct words or phrases."

They go on to say, "There is no nation, except our own easy-going one, that would tolerate such words as..." Ah, those easy-going Victorians. I think a little cross-pollination time-to-time is a good thing. Keeps the language from the knacker’s yard, as it were.

The phrase is a Britishism, if I may extend the appellation to an entire nation. It rings oddly in American ears, at first. Whether it is grammatical is irrelevant: it is an established idiom. It is a useful phrase, much better then "missing and presumed..." It has hope in it. Embrace it.

The short answer is that both "identical to" and "identical with" are accepted usages. My research reveals that the latter construction is older, but the former is not particularly new. The OED traces "identical with" to the 17th century; Merriam-Webster cites a usage of "identical with" from 1922. If "Scientific American" was using "identical to" in the 1920s it is a safe bet that the usage was well established by then. M-W sees a shift from a prevalence of "identical with" to an equality with "identical to" from about 1950 onward. Or should I say "equality to?"

The argument that tries to narrowly define the prepositions "with" and "to" as associative and separative ignore the complexity of both words. (It is perhaps ironic that the smallest words can sometimes have the most varied usages.) The preposition "with" can be used to separate (broke with tradition, done with arguing) just as "to" can be used to associate (come to fruition, came to believe).

And that old thesis supervisor – I think you mean "advisor" – who insisted that the objects being referred to as "identical" were of the same identity was mistaken. One definition of "identical" is "having such close resemblance as to be essentially the same." Identical twins are, in fact, two distinct persons.

The fact is that both "identical to" and "identical with" are in common usage, and neither causes any confusion. If you prefer one to the other, use it.

Just because a "fairly authorative, university entrance exam site" prefers one usage doesn't make the other wrong. They are authorities on entrance exams, not English. Take their advice for the exam itself and move on.