"These days, trading while DNT has a very very narrow definition. A DNT user is not allowed to use sythe to find trades. They can't view the market (they could if they logged out) so if for example someone gets a discord add from a DNT user but they haven't posted their discord anywhere or advertised anywhere except sythe, that would be not allowed. Finding trades through other places is allowed, regardless if the users are on sythe or not and this is generally on discord trading servers.
There are also a handful of clowns who have a DNT but will post a trade offer in a non-market section, that's also considered trading while DNT"
tl;dr - You are not allowed to use sythe to find trades, or conduct trades on. You are allowed to find/conduct business offsite, so for example discord servers not related to sythe are ok.