Subtitles won't turn off

Recently Coop missions have been showing the commanders subtitles even though I’ve always had the ‘Display Subtitles’ under Sound Options unchecked. I did a battle.net options reset and scan/repair with no change. Is there another option or hotkey I’m not aware of I can try changing, an ini.file etc I can edit?
I cannot find any other info. or find evidence of anyone else having this issue when doing a google search.
Otherwise I can only see it being a bug at this point.

I have the same issue and no luck resolving. Other reports say even reinstalling the game won’t help.