ckeditor/ckeditor-dev — pull request #46 by niklam (2013-06-24 10:23:18+00:00)
Title: #9929: [Chrome 23] &nbsp; is created when deleting character and typing common space

It seems as &nbsp; is a result of altering source by checkStartOfBlock()/checkEndOfBlock() using trim(). Changing order of checks in if() checkStartOfBlock()/checkEndOfBlock() are run only when necessary, not every time del/backspace is pressed.