If its been a bit since you've posted, the pinned posts for the mega threads like "News" are now consolidated in the pinned post "Temporary Hexbear Megathread and Event Portal"
Are you using those links to go to the current unlocked mega threads for News?
Antifascism is locked from making posts (but not comments), but it looks like its been locked for 3 years for anybody who isn't a moderator. (not sure why though, maybe to keep potentially important things from not being seen by enough users).
Politics isn't locked for me.
Clicked randomly around the communities list and besides Antifascism, none show as locked.