I thought about this once and came to the conclusion that the problem doesn't exist: Anger is the only thing you can accomplish by typing letters into the sentence I'm writing. If the goal is not anger but to write text only one person can write a sentence at a time.
The solution then becomes really simple: You insert your cursor where you want to edit. You wait for the text and/or background of that paragraph to change color. Light green would do nicely.
Other users will see that paragraph turn red.
The paragraph is now under your control. If someone else desires to edit a sentence in YOUR paragraph that sentence changes color again and the side bar displays a dialog allowing you (the owner) to 1) hand over the paragraph to the new author, 2) hand over only that sentence or 3) ignore the request.
The solution then becomes really simple: You insert your cursor where you want to edit. You wait for the text and/or background of that paragraph to change color. Light green would do nicely.
Other users will see that paragraph turn red.
The paragraph is now under your control. If someone else desires to edit a sentence in YOUR paragraph that sentence changes color again and the side bar displays a dialog allowing you (the owner) to 1) hand over the paragraph to the new author, 2) hand over only that sentence or 3) ignore the request.
Dumb software wins!