It would he nice if you could allow players to give reputation.
How I see it:
When viewing a player you can see Profile, Give and trade. There would be a reputation box.
In the box it could show things like this:
Example's Reputation:
Zenithar (+1): Wow, thanks for the hat!
Zenithar2(-1): User was mean to me.

And making a 3 rep per day so ppl dont abuse it. Also make sure its per IP or per account. Reputation whores boosting themselves is a story ive seen b4 lol.