It would be great if the preview could also evaluate the first field ("Page containing list of pages to leave a message on:") and display the number of recipients the message will be sent to - just like it is already shown after the Send button is hit.
(And while we are at it, including the subject line in the preview could be useful, too.)
Version: unspecified
Severity: enhancement
See Also:
https://bugzilla.wikimedia.org/show_bug.cgi?id=53970