Just tried on a clean install of Firefox Developer Edition (45.0a2) and it still happens. The OS is Ubuntu 14.04 (32-bit), although I also have the problem on Mac OS X (El Capitan).
Steps to reproduce:
1. Open DuckDuckHack project within Codio
2. Open Terminal: Tools -> Terminal
3. Enter commands to push the cursor to the bottom of the screen, e.g.
4. Increase terminal font size: View -> Terminal Font Size -> 16
For me, the cursor is now off the bottom of the screen and I can't see what I'm typing at the command line. The commands still work though, if I type blind.