This thread probably belongs in the
theories section.
Obviously, Quote does technically talk, even though his lines aren't shown due to Cave Story utilizing the "Silent Protagonist" trope, but that doesn't mean he's a chatterbox. That partially depends on how you play the game, but consistent with the "Sigma Male" trope, Quote doesn't really say much of anything except when the player has him talk to someone. We have no reason to suspect that he says more than what's needed when talking to other characters to progress the story.
I think that Quote's demeanor in the credit art illustrations gives us the best glimpse at his personality:
Others may have a different interpretation, but I always felt as if these images portray Quote having a fairly reserved, quiet, and straightforward personality, consistent with the sigma male trope.