The MQ versioning repo is separate from the main versioning repo. So I don't see how one follows from the other here. You can perfectly modify history in the main repo and version that editing in the MQ repo. The main repo will look clean because the history editing is versioned in the MQ repo.
In git, if you rewrite history, you lose information - you can no longer see what things looked like before you rewrote it.
Disclaimer: I use git myself and prefer it. But the hg and MQ bashing in the comments here is unfair.