bbPress

Forum access under membership control. Boards, topics, and replies are access controlled.

A forum is often the thing members actually come back for, and bbPress is the natural WordPress forum plugin. Left on its own, though, it knows nothing about memberships. Anyone can register, anyone can read, and the only access tool is a user role, which is the wrong shape for "gold members see the private board."

The integration puts your tags in charge at every level. A whole forum can require a tag before a word of it is visible. Individual topics can be tagged separately, so a public community can have a members-only corner without running a second forum. Even replying can be gated: reading might be open to all members while posting requires an active paid tag.

Because access follows tags, the forum polices itself. When a membership lapses, the member loses the forum along with everything else, at the same moment, with no separate ban list to maintain. When a support gesture grants a month of access, the forum opens for that month like every other piece of content.

Subscriptions stay intact too. A member subscribed to a topic keeps getting replies while their access lasts, and stops when it ends, which keeps departed members out of your notification loops.