The chin just helps people choke you better. You cant slip out of their grip as easy. Also a big chin is bad for fighting. The easiest way to knock someone out I to hit them on the chin. It makes the head turn and the brain bounce against the skull. The more the chin sticks out the easier it is to hit and the more the head turns.
"The chin just helps people choke you better."
I'm no expert, but I've grappled a lot, and this hasn't been my experience. It's also inconsistent with my second link. Are you speaking from experience, can you support with citation, or are you speculating? I'm happy to be educated, if you can back this up.
I'm no expert just an mma fan. The rear naked choke for instance. Once they get under your chin its hard to slip out. The bigger the chin the more difficult. The chin is like a hook. Imagine a person without a chin. He could just pull his head out. Especially if they are sweaty.
I see what you mean. I agree, "once they get under your chin, it's hard to slip out" - I also agree that "he could just pull his head out" - but in both cases, only if the head/neck grip is the primary grip, and there's no leg/body control.
...which is a long way of saying, I'd rather fight a dude with no chin, and if there were some option to temporarily remove my chin while grappling, I'd still decline, for performance reasons :)
I'd love it if a more experienced MMA player could chime in to confirm or deny our suspicions.