Word 2016 sometimes flags my text as incorrect if I terminate dialog with an em dash AND do not insert a space betrween it and the end quote. Office wants a space in there.

Example:

“I couldn’t possibly let you—”
“Let me? Let me!” His outrage jerked him to his feet. “Since when do I require your permission?”

Every US English grammar guide I've read agrees that a space is unnecessary between a terminal em dash, and the quote mark.

I've flagged this bug for Microsoft, but it hasn't been corrected. I don't want to disable Office from checking for missing spaces, where appropiate.