As for the use of comedy in tense moments, I can understand the argument, but personally see the Han/Chewie moment with the Guavian Death Gang as similar in nature to the OT examples of Han’s line “You’re gonna die here, y’know... convenient” or Leia reuse of the “I love you/I know” as she readies her blaster in ROTJ. An indication that even though the heroes are down, they’re not out, just waiting for the right moment. Keeping calm in those situations, I guess.
But you're missing the most egregiously wrong thing about the Guavian Death Gang scene. It's not just that Chewie's head shake was for a cheap laugh and removed all tensiion and sense of peril from the scene. It's that Chewie was portrayed out of character. Chewie *contradicts* Han, in effect taking the side of the bad guys. Chewie would *never* do that when they're at blaster point, where the bad guys can see that he's calling out Han's lie.
Sure, among friends in a safe environment, like the Med Lab, he'll laugh at Han's expense when Leia rips him. But that's totally different.