Developing a line on fatphobia is a good idea. I do think it would improve outcomes to take a look at how previous attempts to establish lines unfolded and to compare this critically with how irl organizations succeed at doing this. Of course it can't be perfectly emulated because it's a website and not a party, but I do think there are recognizable negative patterns.

I agree that political education is valuable and something a site like this can contribute to. I would respectfully suggest that those interested in developing a line recruit and develop openly, for example establishing a committee where folks know who is on it, why they are on it, how work will be done, and how to get on it. And that you bring people along by announcing the intent, declaring when the process begins, and focusing on how the line (which sounds like it might be bylaws more than a work of theory?) will be shared, updated, and balance education (bringing people along) vs. removal (when people go too far and aren't in a position to be educated). This is not because I am dogmatically committed to bourgeois notions of democratic participation or transparency, but because they are ways to create buy-in, avoid alienation, and improve the theoretical correctness of the line as well as the concrete skill of community management.

Anyways, this is meant to be a constructive suggestion based on irl experience and having founded a (still running) left forum, so I hope it is not taken as venting or unhelpful criticism. Running a site is often thankless.