Forum text being cut off by right sidebar -- cannot read or write forum posts

Forum text being cut off by right sidebar -- cannot read or write forum posts

Hello!
In Projects > Forums, when I access any discussion topic, the text area is cut-off by the right sidebar. I can only read about half the width of the text box, when I am reading, or composing a post.

This happens in both Chrome and Firefox (the only 2 I use).
I'm using a high-res display (Surface Pro 3). Like many Windows 8.x users on a high-res display, I set the Windows options: Settings > Personalization > Display > "Change size of all items" = [highest slider position] (otherwise all text is too small to read).

I have found no way around this. Changing "zoom" settings on the browser does not help.

Any ideas? Thanks!