I'll give some of the reviewers the benefit of doubt and not assume misogyny immediately, it could just be simple projecting.

Keep in mind this just my observations in regards to me being a guy and from conversations with other guys.

Typically your potential partner having MANY past relationships could be considered as a red flag in the male community. Two to even three is just bad luck or testing the waters, but something like four or even more past relationships can and probably will be considered a large red flags by guys who are looking for something long-term, especially if that number is >4.

I've literally seen this all play out before - there was group of friends hounding another guy (out of concern) that he probably shouldn't look for something romantic with a girl that had six relationships prior.

This might be that bias, but on a different scale, although this is just a simple assumption.

(Of course I'm only talking about past relationships and not casual sex, that is a different story, though that may also be of influence)

That and AO3 is more sexually open, due to obvious reasons, so you're likely find more acceptance there rather than FF.net, which smut is "banned".