Checked in 1.28.0-alpha (93f90bf) after the transition scripts were run - the issue persists for users who visit some wiki for the first time and for users who haven't been logged for a long time (also see T140327: [betalabs-Regression] Incorrect count when only cross-wiki notifications are present)

Present in 1.28.0-wmf.11 (rMWce33bcf645f6)
The screen recording is for user Zilant17. I checked in db for hewiki - only five notifications, all seen/read, coming from the same page, all of the same type:'edit-user-talk'

Note:

• The issue happened with three users out of four that I use to test in production
• The issue did go away eventually; login/re-login 'synced' the display status with actual read status.

Change 301382 had a related patch set uploaded (by Sbisson):
[WIP] Moderate notifications

https://gerrit.wikimedia.org/r/301382

This has been marked for inclusion in Tech News, so asking to be on the safe side: Is this just beta cluster, or affecting content wikis too?

In T140836#2539739, @Johan wrote:

This has been marked for inclusion in Tech News, so asking to be on the safe side: Is this just beta cluster, or affecting content wikis too?

This probably affected production wikis too

I don't think this is completely fixed. https://gerrit.wikimedia.org/r/301382 still needs to be merged and the maintenance script in https://gerrit.wikimedia.org/r/#/c/302480/ should be run to take care of the few user accounts that are very problematic.

Change 301382 merged by jenkins-bot:
Moderate notifications

https://gerrit.wikimedia.org/r/301382

Checked in betalabs - all cross-wiki bundled notifications can be expanded and all messages displayed.