That would complicate the UI just to cater to a very specific (and rather rare) scenario.
These messages are generated individually and at (slightly) different times, so it’s not possible to merge them.
Workaround: “Mark all as read” and then logout/login and they will have disappeared.
Ehh… no.
Not really. How many countries celebrate it anyway?
Two colors split vertically is way too specific a case. It would make more sense to have fully configurable colors for each ‘corner’ (perhaps with some color cycling options, too), however I think the customization UI would quickly become unweildly (each exhaust already has two colors, which would turn into 8+)