But if say, there was a Liberal Feminism board, or even just thread and people were posting on there to say that women should be free to make the choice to be strippers, prostitutes, work in porn, I might come along and put across my argument as to why I don't agree. Would that be acceptable? Obviously I would read people's views on it and why they have a different opinion to me, but I would probably disagree. Or would it only be a place to all agree x, y, Liberal feminism.
Yes, by god it would be acceptable, abso-bloody-lutely! Plus it's Mumsnet; the hound that won't be leashed; who could stop it?
With a subforum, if there's a thread on, say, legalising prostitution (Note: there is no single libfem view on the subject); whilst there may be however many posters saying "never, no way, terrible thing to do" and however many posters saying "yeah actually, I think that makes things safer for everyone", you won't get five pages of people saying "anyone who thinks this is a good idea is no feminist" and stifling debate on the actual topic. Because, you know, the very fact of a Libfem section kind of legitimises the idea that you can indeed still be a feminist but not subscribe to every or any one "feminist" point of view!
On trans issues, I suspect one would have to do a lot more than you've described, but that's for another day. Most of all I think you'd have to be almost foolhardily resilient, and that should not dictate whether or not someone gets to engage with feminism on the topic.
Come off it Rat. You have the entire rest of the internet where your views dominate and debate is actually suppressed.
...but I don't want to be put out to the rest of the internet 
That's the thing. Generally radical feminist discourse is derailed or censored. It isn't here. Which is quite nice
I agree, this is absolutely a good thing! It's just been so enthusiastically received that I think change needs to happen to prevent disenfranchising a load of women.
This. If the section was created would dissent be allowed?
Yes yes yes yes yes!!! 