I noticed that this question, like so many on EL&U, garnered several answers that were fairly short, written in conversational tone, and had no supporting citations. Such answers are considered low quality according to official site guidelines, regardless of whether they are accurate, helpful, or upvoted.
Some of those answers got the following canned warning:
We appreciate the desire to help, but please consider either expanding your answer or deleting it. Questions should be answered as an expert would answer them: comprehensively, with explanation and context. Explain why your answer is right, ideally with citations. Unsupported answers may be removed.
Now, I don't believe the verbiage is meant to be harsh, but it was only placed on the answers from new or low-rep users (I haven't verified, but it seems like the cutoff is 100 rep). Several other answers were of similar quality but didn't get the warning.
This seems discriminatory and unwelcoming to new users. (Yes, I know that's a recurring theme.) It gives the impression that the rules are not the same for everyone; that if you can somehow make it "into the club" then you don't have to adhere to the same standards. It's also confusing to receive both upvotes from the community and a suggestion to delete your answer from a moderator.
Ideally, we should be able to keep the helpful "you can improve your answer, and here's how" while losing the ominous "improve your answer... or else".
I think it would also come across better if we disclose the reason their answers are triggering the message while other same-quality answers are not. This might be a bit involved to explain in a comment, so we could certainly include a link. Speaking of which, the links that are already included in the warning (namely this and this) don't strike me as very helpful.
The first one explains notices that are not comments. Maybe the newbie warning comment "annotates an exceptional situation" and is thus somehow not a "normal" comment, but that's as clear as mud, especially to the target audience: users who don't yet know the ins and outs of the site.
The second one points to a lot of discussion about well-intentioned but not useful answers. It actually seems to be focused on how those affect the visibility of the question (via being answered or not answered). But the answers that are getting these newbie warning comments actually are useful (as corroborated by the upvotes). They just don't meet official guidelines.
So yeah, I understand the motivation for the newbie warnings, but their execution leaves a lot to be desired. (You might say these are well-intentioned but not useful warnings. :P)