I don't see why not. Karma isn't that important, and if someone is losing or gaining karma because the small number of people that prefer to see dead threads up or downvote them I don't think it will really change anything. Allowing this to be an optional feature seems like it would be a perfect compromise between people who want to participate in these conversations and moderators who don't want to see them.
I just found out that a new website feature was implemented 2 days ago. If a comment is voted to -4 or below, it and all replies and downstream comments from it will be hidden from Recent Comments, and further replies in that subthread will incur 5 karma points penalty. The hiding, but not karma penalty, applies retroactively to comments in that subthread posted before the -4 vote.
This seems to be worth a discussion post since most people are probably still voting things to below -3 without knowing the new consequences of doing so.