(Passing by after being massively busy!!)
:/ (don't know how to visually type a protruding lower lip).
I do not know either but there are some webpages out there with compilations of emoticons, you can surely find this! X)
So, my summary is the more entries a jam has, the less chance it has of having a reasonably even spread of votes.
Ludum Dare is a rather big game jam, and you can easily get the voting quorum (which is about 20, so, a fixed number) if you review other games. For example, I have taken a look at the last edition (which is 51), and those people that do not reach the threshold are those that reviewed few games, the others generally experience little to no trouble. (Except that the new algorithm still needs some fixing.)
Notice it does both use a fixed threshold and a karma-based default ordering, which hints at it working.