When viewing notifications it is hard to know which ones have been read and which haven’t.
Example
There is a tiny blue dot 
, which oddly doesn’t match the colour of the dot in the left hand bar.
I suggest two solutions:
User clicks on 
and can select Clear read notifications
Read notifications are reduced in prominence (and prominence increases on hover/focus)
Another way to handle this is to have an “Inbox” tab where all new notifications appear, and you must manually “Archive” or clear them after they are read, after which they move to an “Archive” tab.
I like this model because it allows me to easily decide which notifications should continue to appear in my “Inbox”, where they stay on my radar – like a quick list of “things that need my attention”.
Asana also works this way.
I have also been receiving requests for “archiving” and/or “clearing” of individual notifications to reduce the notification clutter of notifications that have been read, similar as described by @Matt_Blais.
Related:
Today I showed our new fibery set-up to my team. Collective feedback: Notifications should disappear after they’ve been read.
Main pain points:
Suggestion:
Archive “read” notifications
For example: Notification Inbox + Notification Archive, which is accessible via toggle on top or “load archive” at the bottom
That would help a lot and give people the “zero inbox” happy feeling 
Agree! Notifications in Fibery are also a big frustrations that our team has. It ruines your productivity 
Notifications is one of the WORST area of Fibery. We know that and do have plans to make it great.
This problem should be solved in the last release
