Originally Posted by Angel
i agree with you there but it's interesting that it's Loki who she had an affair with so it does become complicated. And even more interesting of the fact that Thor cared more that Sif's gold hair was gone than him finding out that she had a lover.
If we think in the range of theory that Sif=Jörð we do not know if he was the only one who she have an affair with, its probably just the most scandalous one considering sides involved. Earth incarnation in loveless, mandatory marriage neglected by her husband/son (it is a miracle that they had Þrúðr together) it is easy to see why she fall in affair with Loki, and probably many others.
As for why Thor cared more that Sif's gold hair was gone than him finding out that she had a lover, well it`s not his business with whom his mother will chose to sleep. But hair-its her pride and beauty and she was devastated so it was his duty to avenge it=).
By the way, I am stile interested in why marvel do not use Járnsaxa at all. It can be so interesting cross culture pairing without need of human part. And it will free Sif as even in comic her relationship with Thor is strange on-off thing.