I replied episode 4 today, which I usually do at least once anyway with each episode, and when the guy who's watching you while you bury that kid in the yard shows up, I was careful to study what I could about him.
Then, I got to the scene in the sewer with the people, and the black guy (well, the one in the kitchen area with the longer hair. Not the guy with the moustache) is almost definitely him. Three reasons for this.
1) He's very careful to avoid showing Lee his face for the first little bit, keeping his head down, washing his hands, etc. He was probably panicking at the time, worried Lee had somehow tracked him down. The only time he looks up is when he realises this was all just a fluke.
2) His hair and body type are pretty much bang on to the dude watching you while you're in the yard. He's also young enough that running like that dude did when Lee spotted him seems easily believable.
3) His ties to Vernon explain why they ALL disappeared at the end when you go back to them. They may be in on it, he may have taken them ALL hostage, who knows?
4) Vernon's bit about "we can protect Clementine better than you" to Lee. Maybe he knows about the dude's plans, maybe the dude really DOES have her best interest at heart. Vernon could easily be the "partner in crime" who ultimately agrees with his cult leader's vision, but wants to find a "nicer" way to go about it all.
In the end though, I'd say I'm pretty much 98% sure it's him. The black guy, I mean. Not Vernon.