I’m old enough to remember the internet before social media and then Trans Orthodoxy came along. It was very common for popular boards to have a Women’s thread or sub forum because women were usually outnumbered and wanted a place where their voices were not drowned out by the majority views and interests of men. Sites that survive from back then often still have them. Mumsnet is a really interesting exception in that being female-dominated from the start it went the other way and has a Dadsnet 
So the women’s board would be set up. A typical dynamic would then play out. Some men would take exception to this and insist firstly that it was sexist and shouldn’t be allowed, and when that failed, that for equality to be served they needed a Man’s version as well. This would duly be set up and there would be an initial flurry of activity as the men involved congratulated each other. A few would try and post something “men’s interest” but as the initial excitement waned they would get fewer and fewer responses and the board would slowly die a death as no one posted.
These men’s boards typically failed because they weren’t needed in their own right as a place to talk, they were just set up out of malice and opposition with nothing to drive their own focus. Men’s needs/interests were already being met by the site as a whole so they didn’t need the separate space. Meanwhile, the women’s board would continue to be relatively active because it had a genuine purpose.
I’m pretty sure if you split sex-based feminism into its own area, a similar dynamic will play out here. The sex-based board will carry the FWR momentum and the gender-based feminism board will dwindle.
Mumsnet itself is a feminist site simply by dint of women talking and helping each other deal with the stuff that crops up in women’s lives. You don’t need a soft, don’t scare the horses feminist discussion board because that’s already covered by the site as a whole. You need a this-isn’t-nice-but-it-hurts-us-and-it-needs-to-be-said feminist discussion board or it has no purpose.