Cannot clear one of Bold or Italic or Underline when all used together on Opera

[Robert]

Found on Opera 12

1. Open sample
2. Clear editor
3. Hit Bold, Italic, Underline
4. Type some text
5. Hit again Bold, Italic, Underline

Result: Bold and Italic are deselected properly, but it is not possible to clear Underline.
Deselect order in point 5 does not really matter, the last option cannot be deselected.

6. Type a bit more
7. Try to deselect Underline

Result: Caret goes to the beginning of the line. Moving it at the end and hitting Underline moves it back to the beginning. Deselecting Underline at the beginning of the line is not possible as well (Bold and Italic works fine)

Another situation:
Repeat stpes 1-4

5. Hit Bold

Result: Sometimes caret goes to the second line. As I think it happens when typed text has very short words (2-3 letters long).

Third situation:
Repeat steps 1-6 (deselecting Underline does not work)

7. Hit Italic Result: Underline can be deselected now, but after it's done, Italic cannot. Selecting Bold makes Italic possible to deselect, but when [I] is hitted, Bold cannot be deselected.

Playing more with selecting and deselecting [B], [I], [U] can produce situation when e.g. Bold is selected (Italic and Underline are not), hitting Bold deselects it and selects Italic and Underline.

Only going to the next line by pressing ENTER key makes them work properly (even when all [B], [I], [U] are selected).

Reproducible at least from 3.6

[Jakub Ś]

DUP of #6585