Not sure if I file this under bug, but upon testing, I discovered that silenced users (for typing too fast) are sent a message saying that their account has been put on hold and moderators alerted. Unfortunately, it looks like the “If a user is automatically silenced, send a message to all moderators.” is by default turned off.
And as I’m going through users who have been silenced, there are dozens and many don’t appear to be bots. 
That’s default off because most communities will see the pending items on the review queue and act on it, with the setting for a PM, and subsequent emails/push notification it will cause, existing for communities where their staff doesn’t visit the community actively.
Did you also not get a review queue icon?
Nope, didn’t see it in the queue either.
This changes the nature of the bug then.
Could you please provide the steps for the testing that you did so I can reproduce this?
Sorry, missed this. I’m trying to replicate now.
I’ve also found some silenced users that were not in the review queue. In my case they were automatically silenced by this plugin
Might be intentional but just wanted to share my experience
OK, so after discussing with our moderator team, this is what we’re running into …
If I go into the system profile, I can see these messages under “Sent.” But otherwise, I’m wondering what’s happening with the above.
Otherwise there are no issues with notifications across the site (that I’m aware of).