So after some discussion on one of the ML's I'm from, I think I have come to what I feel are the two most likely reasons that
Sigyn continually is conveyed or believed to be 'abused' by some on the modern community. - Some folks are confusing Sigyn with the various Signys that appear in the lore. Each and ever occurence of a Signy is conveying a human, mortal woman. Several of these women were raped, suffered injustices, and the like.
- Those who perceive Loki as evil incarnate, automatically assume that He must also be abusive.