Is proofreading quotes actually a real issue 
After all, the error should have been fixed by the quoted user in the first place. Anyway, as long as the AI doesn’t change the context itself — and it does/did make such changes sometimes.
I almost hate to say this out loud, but worrying about changes per se sounds almost like code-based behavior where the most horrible thing that can happen is if x=y changes to x=1 even when the latter one is true too 
But sure. If a quote can stay untouched, just like a code block should be left alone, that would be nice or even great. But is it such a big thing that anybody should use a lot of paid hours to fix it?
Another sure. That is just my opinion and I know there are situations where a quote should be a 1:1 copy.