Is this still being worked on? It's been a little more than three years!

This was marked as being in progress in October, 2020, and it is now April, 2021. I would be interested to know if this feature might be available soon. There is no way to make the reply window taller, and in plain text mode, the editing window is also half width.

It can't come too soon! I am an experienced LaTeX user and I like to write answers in plain text mode. In plain text mode on my laptop, the text entry box is really small, it's painful. I mostly like Campuswire better than Piazza, but I just popped back into Piazza for the first time in months, and the larger, expandable text entry window there is a breath of fresh air. StackExchange has a large, comfortable, expandable text entry window with a preview below --- that's one good solution. Gmail offers a popout editing window --- that's another good solution. The solution in Campuswire is really bad.