D-Bus is a system service that is used by processes to communicate with others. It’s commonly used, but as users we rarely see anything of it. It’s usage for programmers and sysadmins is/can be quite complicated. It looks they want to add a new simpler one. Haven’t heard of varlink before, though
actually its not perfect with comments either. I keep 4 notifications in my inbox unread in case I could find out where I got them, 2 of which is inaccessible because they themselves were deleted and I can’t go back to see what was its parent thread