I noticed yesterday that the edit history contains unclosed tags if a <del> tag is removed from it. See revision 5 of this question's edit history to see what I'm talking about. In revision 4 I put the text "say, 30 minutes?" inside a <del></del>. Then in revision 5 I rolled back to revision 3 (i.e. removed the <del></del>). However, in the edit history for revision 5, the <del> tag is never closed, making it look like the whole second paragraph was deleted as well.
I don't know if this is specific to the <del> tag or not. I have at least confirmed (on this question's edit history) that the problem isn't reproducible for the <b> tag.
