I’ve never met an actual linguist who had any problem with newer uses of terms, or any other sort of much decried colloquial trend.
Me, either. Granted, I have not met many linguists. Most, however, are more fascinated with semantics and meaning than syntax and grammar.
Language is inherently non-prescriptive. Dictionaries and style guide describe norms and collective expectations, and must always try to catch up to language as it changes. Dictionaries catch up much faster, because style guides concern themselves more directly with formal and professional writing norms, rather than conversational spoken language, but both change with the times. They do not set the rules, they describe the norms. There are no actual rules.
Eh, kind of. Many languages have
language regulators or academies that proscribe the language with varying levels of authority. English is somewhat notable for being so widely spoken and not having
any language regulator at all.
And dictionaries do have a major impact on languages. English has changed relatively slowly -- particularly with spelling -- since the invention of the printing press first allowed for widespread publication of dictionaries. Periodically there have been
pushes in English to reform spelling, with varying degrees of success. Mark Twain was a notable critic of the American spelling reforms in the 19th century (though that "Plan for the Improvement of English Spelling" is apocryphal).
If you are clearly understood, your language accomplishes the goals by which you choose your words, you are speaking correctly.
Agreed. If, no matter how you communicate, the idea in your head is successfully communicated to your audience, then then you've been successful. Language is extremely complex and abstract. Much of what is meant is not communicated explicitly. That's why it's vital that we strive to interpret what others say in the most favorable light.
For my part, I have no problem with "they" as a singular, and I would question any native English speaker who doesn't find this exchange perfectly cromulent:
A: I saw my doctor today.
B: What did they say?