It's probably the individual proxy you're using. If it sends X-Forwarded-for, it'll send your IP address. Your best bet is to use a SOCKS or HTTP proxy that does not forward such headers. There are many lists out there.

You're doing this because you got banned from a forum? Lame. That's a great way to get yourself perma banned for evasion everytime they figure out it's you posting again.
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