user tag completion - inconsistent choices on desktop app

I move my mouse so it's not in the area above my chat box, type @ and some letters in the chat box - a username list appears, hitting return gets me the top name in the list.  Excellent.  However, do the same only having left my cursor up there are some previous point... my cursor is no longer even visible at this point, but when I hit return I get whatever name is under it, which is pretty much never going to be what I want.  In case the cursor disappearing is OS-dependent I'm on OS X/10.12 (Sierra).

if I move my cursor, it becomes visible, at that point it 100% makes sense to focus on a listed username underneath it, but please can we not have it pick a name under an invisible cursor, under only some circumstances.  Maybe enough keyboard pilots are out there that we can get a tickybox to entirely disable mouse-based selection, for those less common cases when we accidentally jog the mouse/trackpad, but that'd just be the cherry on top.