Since GTK3, we can remove markups in translatable messages!
Actually, I see one advantage for translators: less possible errors.
One disadvantage for translators: need to check again all strings which used these markup.
It makes sense to remove these markups, by making a real separation of presentation and content.
I filled one feature request and I will look for patching .glade files on trunk for futur Gramps 4.1.