ELL is for learners, yes, but that doesn't exactly mean non-experts. It means those who did not learn English as a mother tongue. Some of these are actually very fluent in English by this point, and quite good at helping other non-native speakers with some of the mindset changes necessary to learn English. Others are moderately fluent, but are still missing some important bits of the language. Either way, the crucial point is not so much the lack of skill in the language as the different mindset — that's why the site exists as a separate entity, not merely "ELU, kiddie pool section".
In general, I simply edit to fix any mistakes I see that are quite unlikely to be a stylistic choice, including SHOUTING, "bad" use of punctuation, evil word choice, and
misuse of back ticks. (I see a lot of mistakes.)
Answers should be as long as necessary, but no longer; as correct in their use of English as possible, and as free from error in what they recommend as can be. Answering language shouldn't be dumbed down too much, but does need to pay extra attention to clarity and avoiding ambiguity or fancy tricks except where absolutely necessary to demonstrate a point concisely. An answer that does not explain should be downvoted, edited, or deleted; an answer that cannot be understood by learners in practice should be downvoted or edited.