Trying to stop spam in a community is like a politician trying to prevent heckling during a speech.
Sooner or later, it’s going to happen.
Far better to have a plan for how to respond to it (from the solo spammers to an automated attack of hundreds of spammers) than overreact to individual incidents of spam.
Pre-approving every member to prevent spam is a solution with a big price tag. It slows participation to a crawl.
A member with a question is frustrated and wants the answer now. If they have to wait hours (even days) to be approved to even ask the question, they will file a support ticket, go somewhere else, or use a competitor’s products instead.
Worse yet, beyond the obvious it’s as hard to predict who will spam. If you were watching the door at a political event, how would you know who would or wouldn’t heckle?
A better option is to ensure you’ve turned on all the spam safety features on your platform, enable members to report and remove spam (to a moderator approval queue), and stay vigilant.
If it becomes overwhelming, sure turn on pre-approvals if you must. But this should be a last resort, not a default option.