Hello Protesilaos. This is not a real bug, but looks like some incompatible changes in org-mode starting from version 9.4. Before the box around `org-priority` item wasn't extended with one additional space:  And after updating to version 9.4 this box doesn't look as good as it was before:  I'm not sure what should be the solution, maybe to report bug to org-mode or disable this box on theme level.