Reply notifications and comments history
On mobile, I get reply notification. Half the time when I click on them, the app fail to go directly to the reply (could be that it fails to load the news, that it fails to unnest the comments, or that the news I commented on recently was put premium only so I no longer have access to read what people replied)
In any case this wouldn't be a problem if there was a place I could go to view a list of my comments and/or a list of the notifications I got.
Mobile notifications are great but once you click on them they vanish forever.