I'd like to see a short comment field that can be filled in any time one bans an IP.

I like this idea, would be nice to be able to ban

username, email, and ip then provide a comment for all three, would appear in one block sort of like when you search and display accounts in the acp.

I would use the IP comment mostly to note any uncertainity I have about banning it. Sometimes it hhapens that -- for instance someone coming in from an institution's IP (e.g. University's IP) -- I want to ban the IP for the time being, but would like to make a comment to myself to remove the ban after a while, so that other trying to come in via that IP (say, months down the line) don't face a problem.