Backtick code formatting + hyphen code formatting breaks

To reproduce:

1. In the markdown editor, type "foo – bar"

Expected outcome:

• the double-hyphen turns into an em dash when you type space after typing the second hyphen (this does happen), and then the code fragment turns into a code fragment when you type the second backtick

Actual outcome:

• when you type the second backtick, the em dash turns back into two hyphens, the space before the first backtick is deleted, and the code fragment turns into a code fragment that starts with a backtick

I'm guessing there's an off-by-one error caused by not being sure whether to count the em dash as one or two characters. Or maybe just broken unicode handling.