Sometimes the person you were sure was fake ends up being the one who shows up. Leave room to be wrong.

First impressions are made quickly and defended stubbornly. Someone can read as insincere for reasons that are mostly style, nervousness or unfamiliarity, and once you have filed them that way you stop collecting evidence. Then something goes wrong and it turns out they are the one who comes. Holding a judgment loosely is not naivety, it is leaving the file open.

Pick the person you have decided you do not rate and give them one ordinary chance this week. Sit near them, ask something, accept an offer. You may well be right about them, and it is worth finding out properly.