It looks like that idea has already been replaced with hiding subthreads rooted on comments that are -3 or lower from recent and top comments.

I just noticed that cousin_it suggested this last year. Also, Eliezer asked:

Does anyone have any strong reasons why LW is better off six months from now if there's a preference option instead of just an automatic behavior to hide such comments? If not, I would just like to see the behavior.

If anyone can think of a strong reason, they should probably follow the link above and comment there.