There are several known bugs with the purple moosage system. Since permies is a forum, not a private messaging system, fixing them has been extremely low priority.
The duplicate moosage today looks to be the person sending it twice, 12 seconds apart. This usually means they had a slow connection and the page load quickly
enough for them, so they pressed the button a second time.
The notification sometimes gets stuck on or off depending on the cookie setup for the browser.