I suspect that I would value LW more if I had the ability to conceal-by-default comments by certain users here.

My LessWrong Power Reader has a feature that allows you to mark authors as liked/disliked, which helps to determine which comments are expanded vs collapsed. Right now the weights are set so that if you've disliked an author, then any comment written by him or her that has 0 points or less, along with any descendants of that comment, will be collapsed by default. Each comment in the collapsed thread still has a visible header with author and points and color-coding to help you determine whether you still want to check it out.