If you are logged in, you can see something like this under each reply in the forums:
By clicking on helpful / not helpful you give feedback to the author about his reply.
Positive feedback will also be added and displayed as part of the user reputation. (Negative feedback will not be made public).
There is also a spam vote option. Here you can say whether you think a post is spam or if it's ok, or if you're not sure. Voting on this, especially on controversial/borderline spammy contributions will help us keep these forums spam free more effectively.