I was by chance looking at the favorites list of one of my most popular deviations today, and there was something like 7 banned deviants on it.
It may be a random pet peeve, but I hate having banned people show up on my favorites lists, or my watched by list. I knock them off whenever I see them. It keeps things tidy.
I also often see people complaining that someone has added their art to an offensive collection. This method should remove those kinds of faves as well, as far as I know. I've done it once on my stock site, and my art was removed from that particular collection.
This seems to be a function that not many people know about. So I took an hour and threw together this tutorial. In dA mold green, of course.
Click on your name at the very top of the page, choose "Settings" then on the left, choose "General" then scroll down until you see "Blocked Users" then add their da usernames to that list, click "Save" then they will be removed from your list. After that, you can remove them again from the list of blocked users.