You may never truly know, but you can avoid scams by reading the stickied threads in the market sections. Generally, there's advice on what practices reduce the likelihood of getting scammed, or else the safest way to conduct certain types of trades. I would also recommend talking to users in the discord to see what their best practices are for keeping safe; the community has some very helpful individuals.
But you can usually know which users are more trusted in the community by checking out their vouches, and examining their account maturity. Typically, users with high post count, older "Joined" dates, and donation statuses are more trustworthy than new users with low post count and low site engagement.
Now, donor ranks are a good way to know if a user is invested in the site, and that typically shows they're straight users. However, we do not give badges or ranks that mark a user as "trustworthy" because the staff of this site will not endorse any users for risk of being blamed if that user scams. We will, however, mark users who we deem to be
untrustworthy with "Trade With Caution" ranks, and we will strictly prohibit a user from engaging with trades on sythe by marking them with "Do Not Trade" ranks. If you see a user marked with TWC or DNT ranks, you can click on the rank and it will link you to the reason they received those ranks. This is where common sense will help you. If a user is DNT'd for being in debt with another user, you probably shouldn't trade them.
TWC rank:
DNT rank:
