When we cancel a TagCreationRequestedEvent or one of the cancellable repository permissions events the message passed to the cancel method does not render in the UI. Instead you get some canned response which doesn't say why the event was cancelled.

For example:
event.cancel("Not rendered")

You can see this when you have an event handler for TagCreationRequestedEvent which cancels the event the UI does not render the custom message the handler cancels the event with. Cancelling something like BranchCreationRequestedEvent renders the message in the UI.

There are good cases for it being rendered so the user knows why it was cancelled.