Italics cause the cursor to get stuck when writing comments on PRs

Hello,

I am on OSX and I often use ALT + <LEFT|RIGHT ARROW KEY> to jump back and forth through words.

Everything works fine when I'm normally writing a comment, but when I add italics to a word then the cursor can't always jump backwards past that word. For example when I type this:

#!plaintext

This is an _example_

And then immediately hit ALT + LEFT ARROW KEY, the cursor will flick to the left-hand side of "example" and then back to the right-hand side immediately. Moving the cursor between typing the second '_' and trying to jump seems to work just fine.