Purely aesthetic considerations, but that would help visually separating neighbour tabs…
When using uneven tabs, I think there should be more whitespace on either side of the tab title. Currently the tab border/tab text space looks roughly one character wide, IMHO it would be better with ~twice as many pixels (cf. spacing in Safari tabs, for instance). The bell icon can of course be displayed in the whitespace since it's transient.
In the same idea, uneven tabs should respect the minimum tab width, so that even when they get a really short title (1-2 characters) they are easily clickable.