I dunno about auto-banning-- that sounds like it could get out of hand pretty quickly. (I mean, I could be a real putz one day and find myself booted on the basis of one day when everyone just had to ignor my crazy-talk.)
The Ignore feature is really good. I think if a ban feature would be implemented that it could only be done by a very high level like saints or something. Also that the ban is like a hold period where after a day or to they could try again. And maybe the more they get banned the longer it is in effect.
Update : It would also be helpful to see who you have on ignore (incase if you want to actually talk to them).