File 1 test:
Select a paragraph and add a comment to it
Select another paragraph somewhere else and add a comment to it
Go back to the first paragraph and select the commented paragraph and the next two paragraphs
Extend the comment to all 3 paragraphs
Remove the comment
The comment is removed from the last two paragraphs it was added to, not the first paragraph
Delete the comment from the first paragraph; the comment disappears, but the text remains highlighted, and when I click to another file in the other editor and come back to the first one, the comment is back
Also: Something a bit strange. I tried simply adding a comment, adding a comment, and then deleting the first one. This does work, but if you mouse over the area around where the comment WAS, you'll get some popups around the mouse about a comment. So Scrivener is hanging onto the old highlighting, somehow, which tells me not all the info about the comment object has been removed.
But... if you follow the above method to reproduce the comment deletion problem (expanding to cover larger area), you will also see the popups as you mouse over the area where the comment WAS attached. I made a video so you can see the return of the deleted comment, and the mouseover popups.
Video link https://drive.google.com/open?id=176GwHh5b7ydZopXQtqbcZTWGO7y5EXY7