https://monero.town/communities

Yes, just create an empty room with only you inside

https://kycnot.me/?categories=exchange

Couldn’t you use HMAC with shared secret key to authenticate messages while keeping plausible deniability? Since the key is only supposed to be known to the 2 parties, the recipient can deduce that a message was actually sent by the sender if he did not create it himself. I think that’s what OTR was using.