My personal bias is towards the "thank you" approach. How to thank someone is open-ended - either via a node, private msg, chatter box, etc.
A couple of reasons for thanking someone I can quickly come up with are:
- The person who helped you out has taken some time out of their schedule to look at *your* problem and resolve it. There is no compulsion for them to do this other than a "helping" nature. The least you could do is spend a couple of minutes to thank them for their help and support.
- I think, more than XP, monks (correct me if I am wrong) get a "buzz" when they know that they have helped someone out of a problematic situation. We are inherently "problem solvers". A simple thank you will let them know that you appreciate their solution/feedback.
- When someone posts a problem, many monks will give different solutions. Not all solutions are elegant, practical, meaningful to the OP's original issue. A "thank you" note will highlight the solution that "best" (NOTE: Best here is not absolute/technically best but only best w.r.t OP's context) solved the OP's scenario. This will also help other monks who may face a similar problem and they can immediately narrow down to the "best" solution.