[quuxplusone]

> There's one or two people that will hold your code hostage until you reply to every little nit. At that point they don't feel like nits.

If the comment must be addressed before the review is approved, then it is not a nit, it is a blocker (a "changes required"). Blockers should not be marked as nits — nor vice versa.

I agree that prefixing comments with "Nit:" (or vice versa in extreme cases "This is a big one:") is psychologically useful. Yet another reason it's useful is that it's not uncommon for perceived importance to vary over time: you start with "hmm, this could be named blah" and a week later you've convinced yourself it's a blocker — so, force yourself to recognize that it was originally phrased as a nit, and force yourself to come back and say explicitly "I've changed my mind: I think this is important." With or without the "nit/blocker" prefixing pattern, the reviewer may come off as capricious; but with the pattern, he's at least measurably capricious.