[DiapDealer]

That's bizarre! I can definitely duplicate it. The span creation alone (where the css provided text-indent attribute is added as an inline attribute) when joining the two lines with del/backspace is baffling enough. I'll have to do some testing to see if this is because of any recent changes, or if it's been around a while, but unnoticed.

I know nobody likes to hear it, but it's another of many reasons that editing in Book View is a bad idea (and probably another nail in Book View's coffin).