This is of course a straw man as Mercurial already has several tools for this (MQ, rebase, histedit), which will keep working as-is even with changeset evolution. So changeset evolution allows things in addition to the local rebasing.
Not only that, but outdated changes aren't shared by clone or pull unless you explicitly ask for them. The full history stays on the server but intermediate commits slowly fade away as users hardly ever pull them.
