If you use the Windows High Contrast Black colour scheme to produce white text on a black background, as many visually impaired people use, then when composing a new topic or replying you cannot see what you are typing. It is displayed as white text on a white background.
This is an oh too common problem on the web. Generally because font colour honours the Windows colour scheme, but background colour has been hard coded to white.
Either honour the OS settings or hard code both text and background. But don't use this halfway house.
Edited to correct an important typo
