TWO FURTHER ISSUES
That specific Developer Notes issue is indeed fixed.
(A) When I try to get the Developer Notes for a Template Page, I get an invitation to append the same value -- In my case "test2=1" -- for both the content areas I create using template page as a template.
(B) I am still not displaying any content on any pages by pasting the given developer's notes from non-template CMS pages into ordinary site pages.
Please see demonstration page in private area underneath.