A members-only community forum
An optional discussion space inside the member hub — never public, never indexed. Start it board-only (the recommended way in) and open it to all members when you’re ready; either way any single area can stay board-only. Members get one digest a week (daily or off if you prefer) for the discussions they follow rather than an email per reply, private member-to-member messages that never expose anyone’s email address, and moderation is built in: report a post, hide or restore it, lock or pin a discussion, or pause someone’s posting while they keep reading. It is the one feature that asks something of your board — somebody has to read it — so it stays off until you decide you want that.