Ianto as a monogamist - definitely! I can easily picture him feeling a certain attraction for Jack for a long time, but he's completely devoted to Lisa and so he ignores and dismisses his feelings for Jack.

By the way, I loved the fairy episode for the simple reason that we finally see Jack showing some genuine emotions, learn about his past and his emotional shell is cracked. I like a Jack who is tortured by living outside of time a lot better than one who doesn't/pretends not to care about anything or anyone. Or maybe that's just me liking to see characters tortured *evil grin*