I'm really, really glad Jeph went this direction-- I was hoping more than anything that this whole thing would develop into a non-issue, although Dora's somewhat arbitrary* "No Hooking Up With My Brother" rule precluded that. I would have been really disappointed had Marten acted any differently and don't really understand why people would begin to call this really manipulative on Faye's part. It's an awkward situation, to be sure, but the only thing she's done "wrong" in this case is to decide that she'd rather break her dry spell than always respect Dora's wishes-- maybe that implies that their friendship isn't as sturdy as they thought, but it's hardly an intrinsically evil or malicious act.
Anyway, kudos to Marten for keeping his ego in check and realizing that this isn't all about him.
*Please note that I am fine with people having arbitrary "deal breaker" relationship clauses-- they exist whether people openly acknowledge them or not. Everyone, including Dora, has a right to choose what they will and won't put up with in a relationship, be it a friendly one or a romantic one. I'm not as bad as the dramatized version of Jerry Seinfeld, but I've broken up with women and ceased hanging out with people over some pretty small potatoes before, so I do have some small amount of sympathy for Dora. That said, I think it's a bit egotistical to think that your close (and miserable) friend with intimacy issues could/would have sex with your brother just to get back at you.
P.S. I feel really dirty for having made a post that long about a webcomic.