What about a 'cancel' or 'delete draft' button right underneath the editor?
I told my users that this would be a bad thing to do, scalability-wise, and they're happy with that - so I'm perfectly satisfied with the plugin and will be paying/donating. In reality, I have no idea what the implications of doing this would be, or how hard it would be.
In case you're interested, what they originally asked for was a 'Cancel' button under the comment editor (similar to the one I see under the discussion editor here). So if you start typing something, a draft gets autosaved, and then you change your mind, you can hit 'Cancel' (or 'Delete Draft', whatever) and the draft gets purged immediately, on the spot.
Thanks again, @hgtonight !!