Hi Charlie, so that line is a little tiny slivery shelf surface:



When it's deleted the surface above it will still have a little edge in it that used to attach to it, that's why it was kind of hard to get rid of it.

At some point I think I might be able to automatically collapse such things when they are initially created, but that kind of automatic geometry modification is a pretty delicate thing, it's pretty easy for it to end up modifying things that were supposed to be there.

- Michael