I was browsing Tik Tok (yes I am ashamed) and saw a video of caver in pretty narrow passage. So that caver took another rock and started to chip in order to widen a little bit the passage, while complaining about not having a hammer with him.
I am a climber, not a caver, and that kind of behaviour would be a big nope in the climbing world (There is a few exceptions where it was done (usually after involving the federation and local community), and it's still pretty controversial)
So I am curious about caver opinion on that practice.
Generally NO, the only acceptable defacement of caves I've seen are bolts to accommodate rappelling down shafts. Of course with commercial caves they have to do quite a bit of defacement.
Not always. I run a commercial tour (approx 5k visitors per annum, so fairly small in the great scheme of things) - one of the things we pride ourselves on is keeping the cave in its largely unmodified state. It's really special to be able to share that with people.
There are stairs to the cave itself, but inside is a completely natural pathway. Nothing between you and the speleothems except a rope on the ground. Lights are an LED system worn on each individual's helmet. And about a bazillion glowworms down in the lower levels over a lake.