After move a bullet from “from dates” below the date bullet into the date, as shown in the pictures below:
the bullet moved turns out this strange style just like date-bullets:
And, no matter where I move this bullet again (even back to its original position), this strange style will not disappear.
This situation occurs on the iOS mobile app and the webapp (I haven’t used the desktop version, but I assume the situation should be the same), with both the system and software fully updated to the latest versions.