ThankYou -- you've learned to say it when you were young. There's a good reason to: it's a GoodThing to remind people that they're appreciated. On a wiki, you can give someone a BarnStar, or simply tell them that they have done well. If they didn't feel appreciated on a wiki, they would do a GoodBye, which is a BadThing. Don't forget to thank people for a job well done.
Please note that it is an AntiPattern to thank people by linking to this page. Write the words separately, unlined. Write, "Thank you for refactoring ... " rather than "ThankYou for refactoring ...". (remember that AbbreviationsAreEvil and PagenamesAreAbbreviations, therefore PagesnamesAreEvilSometimes)
Should be a part of the WikiPatternLanguage, section "behavioral patterns".