User blog comment:Vince Jan Torres/Source code of level pages/@comment-16894369-20140105131243/@comment-4189499-20140110113550

The best way to avoid having that happen is to use source mode when copying and pasting as it ignores all formatting and just leaves the raw text behind. Also, source mode is just better to use in general for this reason, as I can't tell you how often I have had to remove useless spans from articles.