I've been upgrading my blog from 4.0 to each successive beta of 4.15, and I've noticed that I have a lot of "remnant permissions". If I grant permissions to a user, the Select Roles page has multiple entries for "Blog Administrator", each with the label "This role was generated by Movable Type upon upgrade."
Is there any way to easily delete these remnants?

That is odd. You can always select the roles you want to delete and mass delete them. That is one convenient way to clean things up.
I would like to get to the bottom of this. Next time you do an upgrade can you pay close attention to the number of roles in your system and if more are added? Because there shouldn't be.
Hi Byrne,
I get This role was generated by Movable Type upon upgrade." every time I upgrade.
I haven't been loggin/checking the exact behaviours, but if it helps I'll start tracking from 4.2