I think it is a great idea.
Obviously it's lovely to have a focus area where black posters can talk about stuff specific for them.
I also hope in time it might mean that Mumsnet is more appealing to black mums and we will end up with more coming to the site..... this alone would really help counteract the site's racism...
Until then, I hope it could act as a support space where black posters could discuss the challenges of being on the site and unite, if they wanted to, to deal with them.
My only fear is that it might mean less black mums posting actively on the main site, which would make the main site worse not better, in terms of its diversity, awareness and quest to become less racist. But in the end, that's not black mums' responsibility and if the main mumsnet is not a welcoming place then it deserves what it gets. If this happens I will just want to be less and less a part of it.
Right now, mumsnet is borderline for me- it is a majority white space with a mixture of views - some which I find obnoxious because of their racism. I am sticking around hoping we can fight the good fight and change it, because mumsnet has other awesome qualities. But the other alternative of course is to abandon it and join/ create new spaces.