(1) Measure the distribution of comment endorsement for >1000 HN users: how many they endorse, how often they endorse, and how that varies with things like hour of the day, time logged on, etc.
(2) Measure the distribution of "time to endorse" for comments (how long it takes from posting to endorsement), and how that varies with things like hour of the day, etc.
(3) Measure how many comments get lost in limbo because they are never endorsed.
My initial sense is that this is going to significantly raise the cost of participating in HN, which will make me less likely to participate. (By "cost" I mean both the added cost of having to endorse comments, and the added cost of having to wait for my own comments to be endorsed before I can post another one.) But I may be overestimating what the effect will be.