If a node is more than 4 weeks old, then the odds of its author gaining 1 XP when it is up-voted are 1/3 no matter the reputation.

I'm not completely sure, but I think I like this change.

No XP loss if your node is only down-voted once.

I guess I like this one as well

You gain 1 XP for each node you post that at least one person up-votes.

I'm not sure I like this one or not, but it will definitely increase my XP a lot, because I write lots of short comments which very few monks even read and vote on.

For each user, PerlMonks tracks a weighted average of the recent votes that they have cast. Each time you cast an up-vote, your weighted average, $vtavg, is set to 0.1 + 0.9*$vtavg. Each time you cast a down-vote, your weighted average is set to -0.1 + 0.9*$vtavg. So somebody who only ever up-votes will quickly have a $vtavg very close to +1 while somebody who only ever down-votes will quickly have a $vtavg very close to -1. If your $vtavg is positive, then each down-vote has $vtavg/4 chance of gaining you 1 XP. If your $vtavg is negative, then each down-vote has $vtavg/3 chance of losing you 1 XP. No, you are not allowed to look up another monk's or even your own current $vtavg.

I really don't like this change. Not only this punishes downvotes, but it also has a discontinuity at half-half upvotes and downvotes which someone like me might want to work around by casting meaningless upvotes to bring the vtavg over zero.