Also see the same. This is the same as MC-218167 which was fixed but this issue cropped up again since yesterday night GMT
This happens to anyone with a migrated account to Microsoft no matter if they sent a message or not. Also happens to everyone at the same time(with Microsoft migrated accounts). I can confirm it does not happen to people who have not yet migrated
Here is a video. I'll have more shortly from other users. Vanilla 1.18.1 and vanilla client. Go to 0:20 https://youtu.be/FuRv9PhtkAo