User 1234qwer1234qwer4 from ru.wikipedia reports that his notification is only partially displayed.
https://ru.wikipedia.org/w/index.php?title=%D0%92%D0%B8%D0%BA%D0%B8%D0%BF%D0%B5%D0%B4%D0%B8%D1%8F:%D0%A4%D0%BE%D1%80%D1%83%D0%BC/%D0%92%D0%BE%D0%BF%D1%80%D0%BE%D1%81%D1%8B&oldid=77032295#.D0.A3.D0.B2.D0.B5.D0.B4.D0.BE.D0.BC.D0.BB.D0.B5.D0.BD.D0.B8.D1.8F
Notification that have been seen before and then periodically removed. User registered and received notification earlier than January.
2016-03-08 he saw the messages only after 2016-01-20 (it is at the end, after you press the big blue button at the bottom of special:notification)
2016-03-09 he saw the messages only after 2016-01-26
In settings/notification all the checkboxes for web-notifications are included and have not been changed
but here I tried 2016-03-10 to send him five consecutive ping-notifications
before the test. can be seen that the last date 2016-01-27
{F3614415}
this is after. It can be seen that the last date 2016-01-11 - some notifications appeared
{F3614416}
but after thanks-notification again another date 2016-01-13
{F3614460}