I suspected it a while back but Kolyo voiced my suspicions, so he should take the credit really. I'm more of a Johnny come lately.
Obviously I can't be 100% certain, but his speech patterns are similar, as is the easy way he addresses long term members, not the sort of familiarity one would expect from a newbie regardless of how hostile. Then there's his obsession with 9/11, refusal to divulge nationality or gender, his way of attacking anyone American (or British,) for alleged war crimes committed by our respective nations and his spouting of pro Russian propaganda.
If he's not JTT, he's doing a bloody good impersonation.