Making it easy to track users I know would make me read and upvote their comments more. Letting me ignore someone (and making them invisible to the public if enough people ignore them) is another wall.
I think that this would just skew the leaderboard. Everyone would be following the famous members of HN (pg, bucheit, etc), and locally popular users would be distant seconds, while the normal user would make up a long tail of comparatively low karma.
I'm pretty high on the leaderboard (~30) and don't think the order of the top 100 matter. I wouldn't mind being removed from the list. Submissions matter more than comments. Also, the age of your account will matter more as the site grows.
