I just found a really useful answer to a question (that wasn't mine), and have voted it up. Is it ok to add a comment thanking the person that wrote the answer? Or is the fact I voted it up enough?
If you just want to say "thanks" then that is what the upvote button does - an upvote is a thank you. If you want to say "Thanks, your reply for Windows 2008 also works in Windows 2008r2, but you also have to...." then that is also helping others so worth adding.– Rob MoirJan 20, 2011 at 17:46
1A quick look over the site will reveal that the very vast majority of votes, either up or down, are not accompanied by a comment.– John GardeniersJan 21, 2011 at 0:12
"Or is the fact I voted it up enough?"
In a word: Yes.
3+1, Please refrain from using Salutations, Signatures, Thank You, etc.– Chris SJan 20, 2011 at 14:00
1+1 This was also discussed recently in the IT Security beta's Meta: meta.security.stackexchange.com/q/4/953– IsziJan 20, 2011 at 14:52
If you found it particularly helpful and can explain why in a way that illuminates then feel free to leave a comment as well.
+1 Don't waste screen space and clog the db just to give a one-word "Thanks". Jan 20, 2011 at 23:35