A tiny change would make a whole lot of difference to everyone who finds themselves reading the subtitles when there's voice acting. Let the mouse click work during conversations to progress them when the UI is toggled off.
If you wanted to go the whole nine yards you could add an optional visual clue when they've stopped talking. I suggest making the mouse pointer visible again. That way it won't impinge on screenshots.
This way those of us who are so inclined could get a more cinematic experience of conversations. It's a shame that currently it distracts from the great facial animations with something as crude as unnecessary text.