Well, I'm cleaning up in TESVedit, and I've got dozens of exterior cells that are showing edited navmesh for reasons beyond me.
1 - When you finalize an exterior cell, does it mark all the bordering cell's navmesh as edited? Because that looks like what's going on from what I can tell. It shows I've edited most of the cells in and around Falkreath and all I did there was put a house with a door. I used a collision prim set to l_navcut to block out the house and never touched the vanilla navmesh. I'm stumped right now.
2 - I think I remember somewhere that said if you add an exterior door and finalize the cell it's in, you should also finalize all the bordering cells too. Is that correct?