The first photo might look slightly more dramatic than it is, here area two more:

So I tried to remove the gas compression spring of my new office chair from the sockets to send it back. It's firmly stuck in both ends, and I read the recommendation to knock it with a rubber hammer. I couldn't find one, so I covered the gas spring with some soft cloths and tried a regular hammer - and was a bit too enthusiastic. Is this spring still safe to use? I'm guessing/hoping that that's not really the outer wall of the gas cartridge? It is still working, extends and compresses smoothly.

EDIT: so I saw a couple videos about this topic where people removed the holding clip on the bottom end of the gas lift, allowing them to remove the cylinder that I dented from the actual gas spring. I did that on my gas spring and low and behold, I was able to remove it and verify that the dented part isn't actually under pressure - it's rather a duct/guiding rail and pretty cover for the lifting bar that sticks out of the actual spring. So the spring is safe to use once I put everything back, but that outer cylinder might never go anywhere ever again. However, since the spring is still usable, I'm keeping the darned chair and have no more need to get it out for returning.