"Post less" isn't going to help a platform that's still in early days that needs more active posters.

Best I can think of with a 30 second investment of time and thought is:

1. when you post about your perspective/experience, post knowing it is only your perspective. You speak for no one else.

2. when other people post with perspectives that differ from yours, default to believing them

(I also feel like these two cover not just blackness, but women and LGBT+ and even white men who don't have the same perspectives as the majority on this white-and-western platform)

Edit: In response to the four guidelines:

Listen more to more Black people

Sounds good but I don't see how this works in practice here. Anyone claiming to be black on an anonymous platform is 50/50 or more likely to be not black. Reddit had an entire "as a black man" sub making fun of people posing as black and the same problem will exist here.

Post less – and think before you post

See above, not what fediverse needs.

Call in, call out, and/or report anti-Blackness when you see it

For sure.

Support Black people and Black-led instances and projects

I have literally never seen an instance identified as black-led, so not sure who to be supporting. It also seems like it would have a similar problem to a topic that starts getting a bit niche. Like, a movie community will do fine, get more niche to a horror movie community and momentum dies out quickly. Horror aficionados are best off posting to the movie community and non-horror people can deal with the occasional post that doesn't inspire them.

Post something to the movie community about black actors and directors in the horror film industry, or about black characters, or about a horror story that is built on (or appropriated from) a black story, hell yeah, I'm in. Don't spin it off to a different community or instance because most will never see it.