Why do moderators decline "no longer needed" flags on chatty comments?

Question

I primarily land on Code Golf by visiting links to questions from the Hot Network Questions roster. When I see comments on answers like:

Good observation!

or

Wow, impressive!

I tend to flag them as "no longer needed". This is in keeping with my understanding of how comments should work across the Stack Exchange network. The "comment everywhere" privilege page says explicitly that:

Comments are not recommended for…
[…]
Compliments which do not add new information ("+1, great answer!"); instead, upvote it and pay it forward"

I'm a moderator on Stack Overflow, where we appreciate flags on comments of this nature and regularly delete them. In fact, I am even more reserved than the majority of Stack Overflow moderators when it comes to deleting such comments. I will preserve them if I think there is anything of value in them, including observations about what, specifically, is so interesting or impressive about the answer. But comments that say nothing more than is conveyed by the upvote arrow? I think these should go. (And, in many cases, the auto-comment-deleter regex agrees with me.)

Along similar lines, I recently flagged a couple of comments underneath an answer that were discussing how self-answering works. The comments were, essentially (paraphrased so I'm not quoting and don't reveal any specific cases):

How did you manage to post this answer at exactly the same time as the question?

@user I selected the "answer my own question" checkbox while composing the question!

Over 24 hours after the first commenter got the answer to their question, I believe these comments should go. The comments are not providing any lasting insight; after all, self-answering is clearly documented in our Help Center, and the checkbox that controls it is visible to everyone who ever tries writing a question. To me, these are the very definition of "no longer needed".

Especially since I'm primarily looking at and raising flags on Q&A that have made the Hot Network Questions list—I think these deserve extra clean-up and moderation efforts, since they're highly visible and a primary attraction point for new users to your site.

However, I've had a couple of flags recently declined on comments like the ones shown above. I'm obviously not concerned about declined flags, and I'll keep flagging as my conscience sees fit. My question is, do the Code Golf moderators not appreciate such flags? Do you and/or the larger community not believe these these comments deserve to be deleted?

Answer 1

First off I did reject the two flags at the bottom for the exact reason that @ASCII-only suggests in the comments:

For this specific case, I believe self-answering is a very non-obvious thing, so for the vast majority of users, it would be useful information. Regardless, it's certainly very obvious that it's not just a "wow, very impressive". By that, I mean it is not equivalent to an "upvote and move on"

The information is presented elsewhere but it is not really easy to find it if you are asking the question "How did this person answer so quickly". I think these comments ask a question about the answer that has a non-obvious answer and answer it. For me this is the most basic purpose of comments.

Nothing has changed about the post itself which would make the comments obsolete, so I think that they should stay.

I'm not really sure if that falls into the same category as other ones. I certainly think that "Wow +1", and "Good answer" comments should be deleted. If other moderators are of the opinion that those should stay I don't know of it. Overall however I think it is fine to raise these flags, pretty much as you see fit.

They take a couple seconds to resolve and we are not flooded with flags or anything.