Some of my users keep loosing important events when they use the web interface. I finally understood what was happening.

When they want to delete an event, they access the contextual menu with the right-click of the mouse and then delete the event. They assume that the event to be deleted is the one they clicked on, which happens not to be the case: the web interface does not make clear which events are selected and the pop-up does not provide this information either. So I see that kind of request:
[[
POST /SOGo/so/XXX/Calendar/11F5-4CBC5100-B-6BC72480/batchDelete?ids=11F5-4CBCA300-2F-6BC72480.ics/11F5-4CBCAA00-47-6BC72480.ics/11F5-4CBCAA80-4D-6BC72480.ics
]]

Here are my suggestions:

• by default, a right-click on an event means that only this event is concerned
• one can pick several events by using the Control-key and only this way
• the pop-up for confirmation of the deletion should include the title of the event(s) to be deleted, just to be sure