So you understood most of what I meant, but we missed slightly. I agree that irregular verbs might be misconjugated or that they may tend back toward regular conjugations (see for example "to plead" in the legal sense, or "to hang" in the execution sense), but I specifically meant mismatched count. As a stickler, I would sometimes put lack of use of subjunctive or adding it unnecessarily (though the second is pretty uncommon) in the realm of a mistake but that could be because I like it and hate to see it fall out of use.

Also yes that's what I was meaning for indirect and direct object pronouns (to/for whom vs who, or maybe more simply him/her/me vs he/she/I). Here you could also include "myself" or "themselves" or the slightly less natural sounding "themself". I was trying to craft an example of creating a misunderstanding in English but it didn't work as well as it does in Spanish for example where you can accidentally create reflexive verbs with a different meaning. I suppose though you are right: these are not mistakes a native speaker can really make because they have the knowledge that the word is changing.

For countability, I assume you mean the question of less vs fewer, and when you might pluralize words like ”water" and when you don't. That is indeed an interesting topic.

Prestige dialects are not an example of a direction I would like to go, but as a counter I really appreciate that French DOES have the French academy to decide what is proper and what is not.

Im an American, I only speak one language natively because there's not exactly a variety of spoken languages in the Midwest. Since high school though I've been "collecting" languages though and am passably conversant in a few. My wife's extended family is all in France so French has been an important skill to develop. For me, the fact is that "deviations" from the book usually result in losing track of the meaning or losing track of the conversation. English is already hard enough without adding even more irregularity, so I tend to lean in on being precise and I think it's a worthwhile effort. It is a real source of stress when the shoe is on the other foot.