One of the canned messages to reject a suggested edit is no improvement whatsoever:
This edit does not make the post even a little bit easier to read, easier to find, more accurate or more accessible. Changes are either completely superfluous or actively harm readability.
Quite an unfriendly message, if not rude, as has already been discussed elsewhere. I propose that we, reviewers, refrain from using it whenever there is good faith on the suggested edit, and instead write a more kind message to reject the edit, say
Although your suggestion does not harm the post, I fail to see any substantial improvement.
or maybe, for rewording and reformatting attempts,
It is dubious whether the proposed formatting/rewording substantially improves this post.
I mean, you can compose your own and just copy-paste.
Good faith edits that at least partially improve the post, yet have "no improvement whatsoever" rejection votes, and whose true rejection reason I am guessing in the labels:
Good faith edit, rejected, but Muru has written the reason why. This is the behavior I'm trying to encourage, namely, to give a proper reason when rejecting.
Definetly bad edits:
Thus the suggestion
Reserve "no improvement whatsoever" for the bad edits, that really deserve it. Otherwise, do not respond so harshly to a volunteered, good faith attempt of improvement, especially to new users. If in doubt, assume good faith.