Certainly not in the Hyatt forum; there is a fairly active thread there with them and has been for years. SPG forum doesn't allow them IIRC. Don't know about the others. Seems to be at moderator's discretion.

I'm fairly indifferent about the whole thing. I don't think posting them is a great business plan, anymore than posting 'how to' guides for 'trick it' type tickets is. Sure it might generate some views (and therefore $) in the short-term, but you kill your reputation and risk your relationships. Further, nobody will be willing to discuss anything with you, because they don't know if they can trust you to keep it private, so you'll miss out on stuff in the future.