Calling commits "immutable" is thus verging into technically correct, but misleading and thus not useful territory. It's giving people the impression that commits are set in stone the moment they are made, when in fact this is far from the truth and you can go back and rewrite them, insert new commits between existing ones, squash them together, remove them entirely, etc. The only "gotcha" to watch out for is if other people have synced your changes; then you start having problems.