I realise that there is other questions out there about the below (First open one I found is Deleted comments persist in the global inbox), but this is marked status-completed.
I often get the below issue where it will notify me about comments on my question (in this case what appears to be the user re-writing after deleting their comment) that no longer exist.
Also, occasionally, I see comment snippets with text that doesn't match what is on the page when I view it.
Let me know if I should be trying to edit that one to remove the tag indicating that it has been fixed, and add the above as another answer.