Okay, what often happens is that people write a 'rate for rate'-posts, do usually play a few the first game on the list. This do some people knows, and they are therefor really fast to come with replies to those posts, and by doing this they at least tries to get a lot people to play their games. And I can see that it seem to be working pretty well. But are you number 7 or 8 to come with a replay to the post, then chance is much smaller that they are playing your games.
But this not my main issue, but I don't want a system where people shall beg for ratings/feedback. You are welcome to think it's the way it just is, but I have been in many game jams where this is not an issue. It all about making a culture where everybody understand what a game jam is about, and it should never be about begging for ratings.