There's something to be said for being a reasonably well behaved Monk for a long time
... and I don't see how to fairly (or nicely) evaluate coding ability for XP directly. There already is incentive to contribute... with every post, you can get many votes and presumably more points than just those for your daily votes if the content is worthwhile. Put up a little 3 line obfuscated JAPH and you'll get 30+XP. I think any point scheme is bound to have seemingly problemmatic issues but it would take a long time for someone to get to abbot or bishop only by voting... and if they're voting so faithfully, why would they also not feel compelled to contribute to the community they're frequenting? I think the system werks as well as possible as it is.
p.s. Initiate Nail Removal Immediately!