One thing I noticed is that the place where the node happens to be posted has a very big influence on the number of XP points it gets, probably mediated by the number of people who look at the given node. Or, more pointedly, the visibility of a node has sometimes a higher influence on its final XP points than its content.

E.g., nodes far down in the thread hierarchy tend to get less votes, which is unfortunate since they sometimes contain summaries of the thread. OTOH, nodes posted on the Monastery Gates tend to get more votes, probably since they are much more visible.

Also, the chances of a node gaining or losing XP points decrease sharply one or two days after it has been posted (since nobody will look at it anymore - probably because everyone navigates by the "Newest Node" page).

Altogether, this unfortunately means that it is of higher value (at least in terms of XP points) to engage in a lively, but maybe not quite so clueful discussion, than to write a review or answer a categorized question, which probably have a much higher long-lasting value. Maybe one should counteract this tendency by giving more points to nodes in summary/overview areas.

All this said, I understand that regulating the XP system is a big problem anyway - it is a complicated social process that is being measured here, and there is little chance in "getting it right" anyway.

Christian Lemburg
Brainbench MVP for Perl
http://www.brainbench.com