Basic words and body language can count for a lot, it's true. There's also the matter of Ginko's tendency to ramble when he gets stuck on a topic, but he hasn't even fooled himself into thinking that actually helps Joker understand much of anything.

Which is why, in this instance, he'll try and keep it simple. He hums thoughtfully and looks down at the squid pieces in front of him, then picks up the beak and quill and holds them up. "Because... if I eat these, they'll hurt me."

He taps at his throat, and-- conveniently, it's then that the recent dryness in his throat catches up to him and he coughs a couple times. Ginko winces, but sets down the inedible pieces without commenting on that. Joker doesn't need to know that wasn't intentional (assuming he can't figure it out from Ginko's face), it's fine.

Instead, he squeezes the remaining guts out of the mantle and holds them out to Joker. "And the guts make me sick. I cut out what I can't eat."