Really now say you have a hacker running in hot-sim. He's engaged in battle with a blackhammer IC and losing badly. Because of the blackhammer he can't jack out himself or leave the node.
But what if a party member physically removes the comlink from his person.

I dont actually know but I'd say at the very least one hellish case of dump shock.

That's exactly what happens... It isnt like the Matrix Movie where you just die, your mind just has a huge brain fart and the spazzing nerve impulses tear at your muscles and bones, hence the physical damage for dumpshock in this case.
If he was running cold sim, he would have only gotten stun dumpshock damage, IIRC.

TMs have it bad where they are always running hot sim, so its either take damage from the IC or take damage from the DS.

And that would only work with external commlinks.

The only way for you to "save" a hacker with an cyber commlink, would be to either unplug him (if he was using a physical line to his datajack), or to jam him.