The original Termbox design was meant to integrate only the watchlist star, i.e. a single icon button with no text. On wikidata.org Minerva now shows two buttons with icons and a label, which looks almost ok, but the patching CSS that originally moved the watchlist star icon to where we wanted it to be makes the buttons overlap.
On beta, there are even more new header elements such as tabs for "Page" and "Discussion".
When making any style changes to the header we might want to see if T232356 is something that can be fixed along the way.