As far as danger goes, I've never got into a state I couldn't back out of using the reflog - though the user experience surrounding getting there and back could

As far as danger goes, I've never got into a state I couldn't back out of using the reflog - though the user experience surrounding getting there and back could definitely use some polishing. As far as having mutable histories, from the standpoint of someone who has to review and integrate lots of branches from a large distributed team, its amounts to a necessary evil. It's difficult to review and merge anything more than a concise set of changes that achieve their end goal and it's also difficult to have committed such a changeset on the first try. Not having the team rebase out experimental and exploratory commits would be a huge mess and while it's an option to just wait to commit until you're done, that risks losing things, and leads to giant one-shot patches that can still be tricky to review and ship. I'm not sure what workflows hg users that loathe to alter history adopt where they don't suffer from trying to integrate messy branches.