I've seen a feature in other forums (vBulletin) where you can thank a useful post or "groan" at it if you dislike it.
It plays a little to the popularity contest but it's not a bad idea to raise participation.
You can see them being used here for example:
It plays a little to the popularity contest but it's not a bad idea to raise participation.
You can see them being used here for example:
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