Rough translation of problem reported on-wiki:
"When I've read a diff the notification disappears from that wiki, but it returns if I visit another wiki not too long thereafter. If I wait for a while the notification won't turn up on any project. I don't properly know how long that "while" is. I have e.g. got a bunch of thanks from tg.wiki for a couple of days now. (Many airports have been placed in the wrong country, which I found out when tg.wiki had been used as a source for some statements.) I often get these notifications when working on Wikidata and will look up the diff on tg.wiki. When I later turn to en.wiki or sv.wiki I get the same notification about a thank you from tg.wiki again."