I highly doubt Jeph would ever write a Marten/Hanners love interest arc. Stranger things have happened in QC, but I think it's the kind of thing that would earn him massive complaints (not that he'd care hugely I hope, but it'd be a pain to deal with for him) and doesn't seem to fit my own personal understanding of the characters involved.
I think Hanners was just smiling at Marten because he's the closest friend she has, who has helped her to come to some kind of terms with a bunch of her issues. If anything I've always thought Marten was being a bit of a surrogate father when he helped Hanners. And Marten is proud of Hanners because she's pushing her boundaries and (I'd imagine) because visiting the station has made him realize just how far Hanners has come since she was last there.
Maybe Marten's overdoing it a bit - Dora, Faye and Marigold have all helped Hanners in their own ways as well, but he's the only person around to take some credit for it, so I think it's easily forgiveable.
I'm just really, really hoping that there isn't some ...silliness between Hanners and Marten in this arc. They seem a lot closer, and maybe it's easy to imagine that as sweet and stuff, but I suspect Jeph would turn anything vocalized or physically instigated into a prompt for a full on mental regression for Hanners and/or awkwardness between the two, and everything would be bad and we'd all feel bad.
Ed: That's in reply to Kenyahp, should have quoted - that'll be the exhaustion kicking in. Don't want people to think I just type up big reply style messages when there was no original post. I'm not that far gone yet.