I think the last lines of him in the book where he's said to wander the shores in regret and pain (don't have the book near), lamenting might be that bit where folks go like. But look at him, what man should do that, he must be weak.

I agree that that likely has something to do with it. Isn't it interesting how regret and contrition are seen as weak and effeminate, whereas being a bullheaded asshat who sticks to a course for no better reason than an unwillingness to be seen as wrong is seen as strong and masculine? Imo, Maglor's choice at the end of the book has always seemed to me to be one of strength. Maedhros kills himself and puts his fate in the hands of another (Mandos, Eru), but Maglor retains that self-control and exacts his own penance.