My user avatar-icon at top right shows the little green numerical bubble as if I have an unread private message in my inbox.
When I tap or click the icon to pull down the notifications, I see a list of recent public message-thread replies, but nothing about a private message.
Inside my profile, I’ve cycled through all the message views — inbox, sent, everything — looking for an unread message, and nada.
Obviously this is a minor irritant for my “keep your interface clean” compulsive personality. 
Any guidance on why this happens and where I can go to clear it?
Did you start a thread recently? Mods running around putting tags on your thread gets you an automatic private message. Those may disappear once you click on them, but I’m not sure. IIRC, they don’t have much in the way of info on them. It should have had the mod name on the drop down menu.
Other than that, no clue. I don’t think there is a take back option on PMs.
No, haven’t started a thread in a long while. I do recognize the “new tag” activity but this isn’t that.
I suspect it’s related to an offensive post I reported a few days ago, and which drew a mod reaction in the thread. Normally I expect the generic “we agree there’s an issue” reply, but in this case I never saw one. Possibly, for whatever reason, the mod response was sent, but it didn’t go through — was deleted or cornfielded or otherwise not delivered — except the notification widget didn’t notice. If I’m right, I have an unread message I can’t read.
The only weird part is the notification bubble appeared the day after my report etc., so I’m not 100% confident in the connection.
So on the PM thread you initiated, I removed you 23 hours ago so the Staff could discuss. This was after 2 replies right before that. So that is almost surely your green bubble notification.
The bubble delay seems odd though. That could be some sort of cookie/browser issue.
Mod activity on a thread you’ve started (including a post report) sometimes causes notifications, even when it’s been hidden from you. This has happened to me at least twice.
If you go to your user page, in the notification section there’s a button to dismiss all. That clears even notifications to hidden activity.
My “dismiss all” button is gray and disabled because I have no active visible notifications.
I think I’ll have to wait until I get another active notification and then use this button, and hope the hidden thing is cleared in the background.
That makes sense, thanks.
Just sent a PM to see if that helps with your phantom bubble.
Yes, thank you! I skipped reading it from the dropdown and went directly to the profile page to hit Dismiss All. I got a stern warning message, but it successfully cleared the notification.
Thanks!
Cool, at least the work-around fix to this odd bug is easy.