Some tickets (for example Support Request or Bugs) are focus on one small thing being discussed where usually a small number of events are posted.
Unlike for example a campaign where there is a large number of events sent to a large number of recipients, in the case of these "small, self contained" tickets, it makes a lot of sense to see that the ticket was modified when a new event is posted on this ticket.
This is what we sometimes customize in some support request fast input. It was the case in Support Request App, but this was removed in 74fc68a7 , this time it's done at a lower level and such customisations are no longer needed.