Limit the number of upvotes to 1 per thread. So the user has to choose the best comment. This adds a cost to upvoting just like the "N upvotes per day" ideas (

Limit the number of upvotes to 1 per thread. So the user has to choose the best comment. This adds a cost to upvoting just like the "N upvotes per day" ideas (which I like a lot).