The help center for When shouldn't I comment? states
Compliments which do not add new information ("+1, great answer!"); instead, up-vote it and pay it forward;
which means comments like "thank you @XYZ" or "thanks, that's it" constitute as noise and hence, non-constructive.
Two of my flags for comment cleanup have been declined with no added explanation. Both of them were raised for completely non-constructive comments:
The first comment was posted on my own answer by OP (answer already marked accepted). Regardless, why are they retained on the posts?
I'm not yet aware that Community moderator bot can decline such flags so it is my assumption that a human moderator declined them. Why did they do that is precisely what I want to know?
I should make it clear that my earlier similar flags were marked helpful and usually, all of the corresponding comments got deleted. The aforesaid ones seems to be exception here. That's why the title reflects: "haste or prudence".
Note: I, at the moment, do not find the need to link the posts behind the comments. Should the links be requested for better comprehensibility of the post, I may consider providing them.
As for the moderators, those are the recent two comments declined against the reason 'not constructive', so you should be able to see them easily in my flag history.