Comment 32 for bug 584632

Can we assume that this is an HTML problem only? If so I have failed to find where it is clearly stated.

I am not sure if my remarks below will be of any help to those working on this bug or users who end up here.

I seldom compose with HTML and don't see this bug with TB 3.1.2 on a G4 with OS X 10.5.8.

However, I did have a difficult to track down font issue with an identical G4. I eventually discovered that most of the considerable fonts in
/Applications/Thunderbird.app/Contents/MacOS/greprefs/all.js were set to zero size. I removed many unwanted fonts and set all the others to reasonable sizes. This cured my problems with this G4. The other identical G4 has not had the problem - on checking I see that all its font sizes in greprefs are reasonable. Although the G4s are identical their TB update histories may be different ie fresh installs vs updates may have varied from time to time.