I have not yet searched the bugs-database, but I have just been notified that selecting multiple instances (by control-clicking) of recurring items in the web interface and deleting them will delete the main/all instances of the selected items.
Performing the operation when only one item is selected produces a popup window with a dialog in which one can choose to apply the action on all event or just on the selected event, I believe the same procedure should be followed when multiple items have been selected (by control-clicking for example)-- users@sogo.nu https://inverse.ca/sogo/lists
