Yeah I think he stopped laughing because Juda and Daath are clearly in love now, not just "bound against their will" like in the beginning. Idk if it's about Juda or Daath tbh, it could be Juda, that's why he said "until his soul bond comes and he throws me away".
I agree on the truly in love part. Maybe it was someone else that Juda knew and the situation still smarts? i just cant wait for the mystery to be unravelled. We know from petit mignon that he continues to be a friend of theirs so of course all 's ok in the end but he seemed to have a hard life. would be nice to see him settled too :)
Or at least with someone else , definitely not Daath. The kiss was more a reaction to his words, i think.
Besides, the other guy said he is not smiling anymore, and if that was the case , he probably protected his heart by being all happy/ understanding for them but in reality it was eating him .
And the merchant was also in Will's face for something...