This is something that bothered the heck out of me on the developer.force.com forums wherein the person who answered the question then prompted the OP to mark the answer as solved in what is thinly-disguised self-aggrandizement.
A recent example of this is here: https://salesforce.stackexchange.com/a/49461/2602
My inclination is to stamp out this behavior with a comment to the comment:
"On SFSE, the etiquette is not to prompt the OP to mark as solved unless you have been engaged in a back-and-forth through comments/chat to get to a solution. Worthy solutions get up-voted by the community."