I wonder if those "ICO managers" or whatever they're called (the ones who create ANN threads on behalf of various shitcoins) could abuse this.

E.g. wait for your competitor to bump their thread and then bump 50 of your threads immediately, knowing that the competitor can't do anything about it for the next 24h.

Come to think of it, just create 500 dummy ICOs and bump anyone you don't like off the front page. Much harder to do that when there is a more tangible cost, like a merit.