@aldobelus @colegota I monitored my Notifications in # for some days, and today I thought that I found a bug: I saw "2 mentions", but Notifications timeline didn't show me anything that I didn't see in the morning.
I searched in logs for "NewNotification" and found out that in this case the two mentions were expected: 4 days ago I was mentioned by some user at mastodon.social, but only today I got two copies of the same note/mention: from mstdn.io and from loadaverage.org. Naturally these two new mentions were collapsed with that 4 days old mention, and this is why I didn't notice them...