I suggest positioning the keyboard shortcut icon right after the Emphasis icon, also called the Italics icon, which looks like this:
I think it would look a little bit ugly there, but I don't care about that. What I do care about is the user experience factor. The proposed keyboard shortcut icon would look a little bit mean there, which would give users a visual cue that it's OK to be mean on the website, which is not a good design from a community perspective.
Stack Overflow has both Graphic Design and User Experience Q&A websites, so I would expect that suggestions like this one would attract quite a bit of professional interest on the Stack Overflow network generally.