Kind of an easter egg. I was so surprised to see that dark elf, who are supposed to be in Riften jail (because of me) to attend my wedding. He said that he was "always happy to see me". After the wedding he returned to the jail by himself. I was SO sad. Damn thieves guild.

On my one character that joined the TG I deliberately failed that part. So he stays in jail for the rest of the game?

Has anyone tried sneaking in and releasing him? Seriously, the player can get off with a day of jail for murdering a city's worth of people, he gets a life sentence for stealing a damn silver ring. I am not joining the TG anytime soon.

I've tried that, I've terrified him out of his cell, I've furied him into chasing me. Nothing does the trick. The only way to do the TG without locking him up is to lose the ring.