Fairly self-explanatory really. I would like the ability to completely hide selected users' posts from view.
Not an original feature (I thought of mentioning it after it was mentioned in passing in another thread for example) and other forum software provides this feature (phpBBs calls it an Enemies List).
I realise there is the karma system, designed to (presumably?) allow forums to police themselves, but I think the ability to have a personal blacklist would be very useful.
Could always make it premium only or something...