I also enter late. There seems to be no disagreement here. The people who are concerned with the laws of grammar do not like "and so". And I think no one likes

He want to the store, and but he bought nothing.

The people who like "and so" are pretty much saying "It sounds fine" and "People use it."

That discordance is common. It's perhaps of interest here because the standard rules of grammar rarely address this issue.