The happy medium I've found is to clarify my level of preference; whether it's a "nitpick" or an actual "change request". I communicate that you don't have to update the PR just for nitpicks, but that if you're updating it anyway that they might be good things to also change.

A nice practice is to finish all such nitpicky comments with the strength of your opinion / how much you care.

This way, if most of those are "very little" then it's up to the author to decide whether to do it or not, and they don't have to wait for you to circle back about it.