It would be cool to have RSS feeds on a per user basis. I'm thinking mainly posts but comments would be fine too. Something like http://www.metafilter.com/username.mefi/user/posts.rss and http://www.metafilter.com/username.mefi/user/comments.rss. It'd be a great way to keep up with people whose stuff you enjoy (like everyone's favorite) w/o getting lost in the volume.
Maybe this has been discussed, but Can we make it so only external (non *.metafilter.com) links open in a new window? I like the preference setting for new window but it can be annoying when it's a metafilter section (i.e. a contact).
How about a proper RSS 2.0 feed? The existing .91 feed doesn't provided authors or even datestamops. Also, the existing ATOM feed doesn't validate properly and doesn't work in the two RSS readers I use (NetNewsWire and Thunderbird).
Are we adding stats for AskMe to a user's info page? That is how I mostly keep track of threads in which I am usually only marginally involved. If this has been covered before I openly apologize.
Probably been mentioned before, but how hard would it be to link check on a post to ensure no double posting? You could even mock the poor soul!