After clicking delete on a user while in the admin control panel a box pops up asking "Are you sure you wish to delete this user?", can this be changed to "Are you sure you wish to delete the user
username?"?
Yes, I accidentally deleted a forum member

This seems like a very logical safeguard to me. I can definitely see why this slight change would improve the quality of the confirmation by orders of magnitude.
We'll also likely have soft deletes for users to help prevent this kind of "oops" moment too so that users can be restored (though there will still be the option to "permanently delete" - probably a third button on the confirmation dialog).
Hi,
Your feature suggestion has been accepted as a planned feature to be implemented in MyBB 2.0. Thanks for your contribution!