Comment 8 for bug 972279

It seems I spoke too soon. If you go to the Select Font dialogue and change the font and/or size, all instances of Konsole update to the selected font/size while the dialogue is open, but sometimes, and sometimes not, bold text isn't displayed as bold. When you save the changed font, the current instance acts in the same way as when the dialogue was open. However, if you start a new Konsole instance by entering "konsole" in the previous instance, the new instance correctly displays bold.

I'm not sure if this was the case or not when I opened the report, but the problem is much less severe than I thought. The problem now is that the new setting doesn't apply to the current instance. It does eventually apply to new instances. When clicking on an icon in the panel, the new setting takes effect after the current instance (where you opened the dialogue) has been closed.

TL;DR: Changing the font setting causes bold text not to be displayed for a while.