A. Width restrictions suggest making the async branches a separate diagram.
B. Be consistent on placement of inherited versus added methods. Always list inherited first? Different fonts, as suggested, might be good.
C. After discussion here, and revision, open a doc enhancement issue on bugs.python.org.
I managed to have a nice layout to have all the ABCs in this module on one diagram. I'm joining three versions to this mail. I'm thankfull to all the people that gave my their opinions. However, I insist that abstract methods should be shown first (in italic, witch is the standard in UML). And about parenthesis, it's a standard in UML to represent methods; so even if it does'nt add anything meaningfull in this situation, I prefer to stick to UML conventions as most as possible.