What shipped
You can delete both scheduled and delivered emails. Deletion is permanent — no restore. That warning is intentional: a time capsule you regret should be removable, but we do not pretend soft-delete is the same as sealed forever.
The deeper comment thread
The most important reply was not about the button itself. Someone asked the hard sustainability question: if the service is free, how can we trust a letter scheduled four or ten years out will still arrive?
I answered honestly: donations had covered costs with headroom; operating costs were manageable; and if we ever needed a sustainability model, we would communicate before anything broke trust. That conversation foreshadowed the year-one update and later pricing chapters.
Decision
Ship delete with a clear irreversible warning. Treat sustainability questions as first-class product trust, not off-topic.