This started as a "How did this happen?" post, but in asking the question I ended up figuring it out, so I'll explain in case someone else runs into it.

I had what I thought was an RCP view of a soffit. I cut a section through the fascia and the section displayed upside down. Text read correctly but the building was inverted. Turns out what I though was a ceiling plan was actually a detail section (looking up) created off of a building section. From what I can tell, when you start cutting additional sections from a detail section view, Revit loses it's frame of reference for what's up and down and just rotates the view as it's literally shown. Regular wall or building sections don't seem to do this, only detail sections.

The lesson here I guess is that if I need an upward looking view of an area not covered by the typical RCP views, it needs to be created as an RCP and then referenced with a detail section cut.