I'm not making that claim, and freely admit that I am utterly ignorant about mercurial. I'm merely demonstrating that, contrary to the author's assertion, it's possible to use git without deleting branches and still have a meaningful way to measure whether a branch is "done", and it's the common-sense measure of "has it merged?"

You can change your mind and turn a 'bookmark' into a 'branch' and back again. you can also fold your branch into another one and pretend it never happened. Or you can pick your branch up and place it somewhere else in the tree, or...