I have been rather disappointed in how she is portrayed in the comics from what I've found on her. I believe she was handled extremely poorly by the writers, as much as by Loki himself. Like it was a bunch of men writing her who didnt know what to do with her, and so just made her a "stepford wife". The more i find about the mythological figure, the more I think she really has a lot of potential in the MCU as a character, if handled correctly, and not portrayed as an unloved abused wife who blindly stands by her man, but as a woman who is caring, and does what she does out of love and compassion, not just because she is married and now she has to do what her husband says and put up with abuse and abandonment. That is just such a ridiculous premise to use for this character when you take into account the whole ordeal in the cave in the myths. There is no way she could have stayed with him, and try desperately to spare him, if she didnt love him. And then consider what led up to that, to keep it together throughout that, Sigyn is well... an AMAZING woman and character. This is NOT a weak woman.
The differences in personality between comic book Loki and MCU Loki as set up in Thor, I think would allow for a much more believable love story between the two than was done in the comics. There is so much missing about myth Sigyn, that it's hard to know exactly how things were between them in that context, and I feel like the comics depictions of her are probably very far off from what was initially intended by the myths.
Anyway, I wanted to share this article on Sigyn, I am not of this faith, but I found it to be a really wonderful insight to this "goddess" and a lot of what she says here is how I'd like to see Sigyn portrayed if we ever do happen to get her in MCU.
The name "incantation-fetter" is a particularly interesting name to be given, considering who she is married to, no? (as noted near the bottom)
also the wiki page on Sigyn
and there is some good stuff on this website as well, but I freakin' LOVE the image on the right there...