Oh yep, looks like they're explicit about it being allowed but not their responsibility if you get ripped off.
"What types of trades are allowed but unsupported? Eligible cross-site trades/Flight Rising to Flight Rising trades that are negotiated on a third-party platform (Slack, Discord, etc)"
Re: brightmyth banned?
(Anonymous) 2023-03-31 03:45 pm (UTC)(link)"What types of trades are allowed but unsupported? Eligible cross-site trades/Flight Rising to Flight Rising trades that are negotiated on a third-party platform (Slack, Discord, etc)"