Sam really should have known better with Suki, shouldn't he. I've always assumed he's just jealous, but Sam's not usually that unprofessional, surely?

Sam's motivations are often a bit obscure in this ep, so really it's open to interpretation! Personally I can't see why Sam would be jealous of Suki, not sexually anyway, unless you're seeing the scene through slash goggles, in which case, fair enough ;-) But to me this is probably the LEAST slashy episode in canon (with the possible exception of Roger sliding his arm behind Sam's back when they're sitting together on the sofa), so I don't see it as sexual jealousy at all.

My guess, FWIW? Sam's envious of the ease and confidence with which Gene swanned into the party (when he himself had great trouble getting into it), and also indignant because for Gene to be bringing a hooker along on an undercover op is just wildly inappropriate EVEN FOR GENE. And of course Suki herself looks ridiculously relaxed about the whole thing, whereas Sam is as you say tightly wound with anxiety. So, he's snippy, and it comes out as sounding like a verbal bitch-slap to Suki, who is understandably peeved.

That's my take, anyway, but YMMV of course ;-)

(And thanks for the lovely review ♥)