1. Edit [[mw:VisualEditor:Sfioj]] in VE
2. Make a selection such as
   
   These [words are] very bold

or

These wor[ds are ve]ry bold

3. Click the "Bold" button on the toolbar

The selected text goes extra-bold, in Firefox 21.

I should mention that in my case, the font is Arial, which has an extra bold "Arial-Black" variant.

Version: unspecified
Severity: normal