Chances are you are safe to delete the accounts listed. They have more than likely been banned and are running under a new accounts now. And once those get banned - it's an ongoing cycle. Feel free to delete them.
I've deleted mine numerous times for that very reason, then it steadily fills up again.
If you ever ignore an actual player for a reason - be sure and use the "note" feature so you can keep that person on ignore. I have a guy that cheated someone for 40k gold on a werewolf bite on mine, and plan to keep him there.
Hope that helps!
I didn't think my hangover was that bad this morning until I spent 10 minutes trying to log into my old Etch-A-Sketch