The xp can be just good luck. If you flip a coin 50 times it might turn up heads 50% of the time, but the first 10 tosses might be heads. update: lemming might be right...you get all kinds of extra goody exp early on, like voting-out bonuses.

The XP nodelet is there when you gain or lose xp, or when you have votes left. Xp losses and gains only appear once and are lost with each page load.