As mentioned in this forum post, I've made a change on the beta server in the way messages are actioned on the mailbox screen.
On the regular server, when you select an action on the mailbox screen and click "Do", it's performed on ALL selected messages in the folder, even if some selected messages aren't currently visible because of the current view or search.
Currently on the beta server, when you select an action on the mailbox screen and click "Do", it's performed on the intersection of selected messages, viewed messages (eg the All / Unread / Read / Flagged / Selected), and any search criteria currently in operation.
This has been discussed previously, and I think this is quite a good idea, especially because the current approach seems to result in unexpected messages being deleted.
There are one or two slightly odd side effects of this change as mentioned in the forum post that I'm looking for some feedback on.
Update: This change has now been rolled out to all production servers