When selecting messages in the Gallery view, the double checkmark icon that is the 'select all' button is misleading, at least to me. I managed to delete all my messages (and was thankfully able to recover some) because I clicked the select all button thinking it would confirm the delete. Then, not noticing that all my messages were now selected I hit the trash can icon to confirm the delete and poof! No more messages. I'd recommend a different icon or some text or something indicating what the select all button is.