I see the merit in ensuring new users learn to edit clarifications into their questions, but I'm a little worried a warning isn't necessarily the best approach, for three reasons:
- As you pointed out, there's a variety of cases where the warning won't be applicable.
- A higher-rep user may already be editing the clarifications into the post (which as you mentioned is frequent). Odds are the edit we asked the new user to make endends up discarded.
- It might not be obvious to a new user what the warning is asking for (although this is something we might be able to address with copy).
I'm not sure what the best approach is here (I'd lean towards encouraging new users to pay more attention to the edit summary and inviting them to learn from it), but I don't think a warning is it.
I'm going to mark this as status-declined for the time being, but I'm happy to hear counterpoints and revisit.