So I will repeat myself: ALL of you who are whingeing about Sedin doing wrong: you ALL are wrong. From a meta perspective, he is the knight, who is supposed to idolise his love, and who is supposed to be faced with adversity.
He is NOT supposed to be beholden to some modern (well, actually, sort of antiquated) either Asian concept of duty, or American Christian version of the same). I guess you all heaping opprobrium on him can be seen as you holding him to a higher standard than the obvious cad prince.
But the thing is, the author/writer is doing it correctly here. It's fully correct for the knight role to be this extremely romantic.
You all should read Johann Wolfgang Goethe's The Sorrows of Young Werther (1774). That will give you a bit of perspective. I mean when that one was in full sway, people (readers/fans/idiots) actually killed themselves - and dressed like the love-struck schmuck of the story (and I can tell you his clothing sense was not up to par ...).