What is causing Word to start selecting text while I type?
I asked and answered this question over at SuperUser. It turns out to be a Word shortcut for extending your selection, bound to F8. It only happens to me on the MacBook Pro touch bar, because of the much more sensitive function keys that I can brush when I type 'y'.
You can disable this shortcut by going to Tools &gt; Customize Keyboard, selecting the category &quot;All Commands&quot;, searching for &quot;ExtendSelection&quot;, and clicking Remove for the F8 hotkey.