Based on talking to Oscar at drop in this morning, I have a proposal for the much discussed "reading options":
We replace the light/dark mode button with a reading options button using the Aa symbol (semi-universal for that purpose.) It will open a dialog where we can have light/dark mode (re-implemented as a three state with browser default / force light/ force dark) and anything else that gets implemented like line-height, font size, etc...
The Bust/User menu will stay Runestone only for now, but is still a possible destination for other controls less directly related to reading settings.
Andrew