Blasters are likely much louder than we perceive them as the audience. Just like how guns in the real world are unbelievably louder than guns on movies. Think about it, blaster bolts literally explode on impact. The sounds of a fist fight or a flamethrower would still be a quiet alternative to blaster shots. Now, is it a bit ridiculous that nobody heard Chewies growls? Maybe, but it's also worth pointing out that everyone in attendance was also very, very preoccupied by Vader's arrival.
Star Wars is honestly kinda low tech in a lot of regards. It's kind of a weird blend of extremely advanced technology in some areas, and shockingly far behind even modern day Earth standards in others. Chalk it up to being Sci-Fi originally written in the 70's and 80's.
Even then, I'm not sure how you would "silence" a blaster. The whole point of a blaster is, well, the "blast" part. They're weapons designed around causing devastation.
As for your point about stun settings, not every blaster is known to have a stun setting. And presumably, a stun setting wouldn't be sufficient to get past the Mandalorian armor worn by Boba Fett. We've seen Clone armor is sufficient to shrug off a couple stun shots, and Boba's armor is actual beskar.
Granted, all of this is me just trying to rationalize how the comic was depicted. None of this is given in the context of the issue in question, but it is all internally consistent with what we know of Star Wars.
Plus Boba has tons of other silent weaponry at his disposal like darts and such. Whatever, itís just a stupid little scene from a comic. Borderline irrelevant IMO. And Iíve been very critical with the whole Disneyverse.