Interesting. If you hit the Post button on any page where a feed appears (home, bookmark tags, your own page or someone else's page), you get the new Post screen.
If you do it from Notifications, Search, Settings, etc, you get the old post screen.
Tabletop, video games, sports and maybe someday some other things if I get the ambition to learn.
My only cohost meta tip that's worked for me is this:
Or a text document can work too, but I like having it on site in case I post away from my computer.