He's still got the body of some guy he took over ages ago, so presumably he doesn't have to worry about running into his double. But the most interesting thing is that since alchemy isn't used in this world, that would mean Hohenheim is not London!Ed (and Al's) father at all. They're entirely unrelated. Which I'm guessing is why Hohenheim was surprised at being called father.
I'm a little disappointed that my first theory about Envy proved accurate as opposed to the new Envy-as-Hohenheim's-younger-brother-and-E
Sue me if this has already been discussed, but I didn't see it and this seemed like a good place to purge the mini-mysteries still straddling my head. There were more, but I was rudely interrupted and misplaced them. ¬_¬