(sorry for sending a bug report without details ) Terminal-0.4.7-1.fc15.x86_64 When I increase the font size in Terminal and then decrease it back, the information for window manager about the granularity of resizing is not updated. So window manager cannot resize Terminal window by 1-character steps, but sometimes two or three characters at once. Also the window size reported by window manager (Sawfish in my case) is incorrect, and probably refers to what size in characters would terminal have with the bigger font size.
Fixed in master.