Sorry to harp on about fonts but I can confim that the font display issues can be toggled on and off by
reverting to the Nimbus mono font. They do not appear with the additional DejaVu Sans Mono font that I installed
to combat the issue.
Ideally monospace fonts should be used in terminal emulators. Nimbus is possibly a problem because it is a PS
font as opposed to a mono TTF.
Having said that, you can use non monospace fonts but the results are unpredictable.
DejaVu Sans Mono has the following advantages:
Another good TTF terminal emulator font is DroidSansMono.Sans Mono[edit]
The DejaVu Sans Mono typeface in particular is suitable for technical work, as it clearly distinguishes "l" (lowercase L) from "1" (one) and "I" (uppercase i), and "0" (zero) from "O", unlike the more widely available Monotype Courier New.[11] A derivative of Sans Mono, Menlo, is provided by Apple with the Mac OS X 10.6 operating system.
Monospace fonts are used in an attempt to make code output more legible.