I think that I found next issue, but first:

I can confirm that issue(2) form my last screenshot is gone, thx

on looong ss below (sorry but I joined couple of sss to one to show you something). Two activities: one is displayed 4! times and second 3 (A,B,C) times.



I didn't understood why number of replicated activities is different and then I found a difference between them. ABC is pinned and this is somehow causing problems. Activity displayed 4 times was added just after the pinned one.

When I unpinned ABC activity everything went back to normal again. In my case pinning feature is important so I have a hope that this is not a big problem to resolve.

There is still a problem with replicating activities and displaying them one to another when the activity is commented before other(new) activity is added (and this will be a common situation). It looks odd I've understood what you wrote that it should work that way, but maybe you will find some way to override this, hack, tweak