[vladvasiliu]

I don't understand what you mean by your first point.

The delete button I was talking about is in Outlook running in a browser: https://i.imgur.com/k4ejdw4.png

Pressing the delete key on my keyboard brings this up: https://i.imgur.com/SBVkpVf.png

Clicking delete doesn't send any notification to the other side, where this account still shows as having accepted the invite (the other side is a different Office 365 organization).

[noisy_boy]

That is interesting. I'm using the PWA on Linux - I can't share a screenshot but basically pressing the delete key shows two buttons: Cancel and Decline Event? - I don't get the Delete option like you do.