We're still having the same issue we reported in 2019 -- people trying to insert an em dash from the special characters menu are accidentally inserting a horizontal rule because they look exactly the same.
Since you now have a separate HR component in the embed bar, can you just delete that button from your special character menu?
| Categories | User Workflow |
While we did not remove the horizontal rule from the special characters menu, we did make it easier to search for specific characters and we display the name of the character on hover which should resolve this issue.