1. A simple "Select * from database WHERE ip='Insert your IP'" Would simply remove that, i can ban or mute you. Bans would block you from site, mutes would just stop from contributing anything... Also go ahead, you wont see it..
I could use a proxy though.
Sure, I could do the same thing on otc, but it would require a LOT more effort.
Fyi, I'm not trying to badmouth your site or anything, but this is something that should be worked on. If I was about to scam someone of, say, 1,000BTC, I could go on your site, give myself an insanely high rating, and before you'd realize that it was inflated, I could give the link to the person I'm scamming and get my coins.