Thought I'd activate this feature whilst I was having a mess about with the forum.

Whilst viewing a thread, if you look just under the number of posts a member has made you will see a small green/grey/red square. This represents the posters reputation.
If you click on the square you can leave positive or negative feedback on the poster. This all counts towards the users reputation.
Number of posts and length of membership also affect reputation.

Any questions?