I think TripAdvisor experimented with this back in the day. E.g. they changed the size of the text entry box and saw that: (a) smaller text boxes got them a la

I think TripAdvisor experimented with this back in the day. E.g. they changed the size of the text entry box and saw that: (a) smaller text boxes got them a larger number of lower quality reviews. (b) larger text entry boxes got them a smaller number of high quality reviews. Even the size of the text entry box changes user perception of how hard it is to contribute, and how much to actually write. So I am guessing there is still lots of interesting UI innovation in these areas...