Right now there's a "No Comment" radio button in the auto-comment dialog for deleting a question in Review-beta. However, it's possible to just vote to delete and not leave a comment by hitting the delete button. It seems like it would easier to use if there wasn't a "No Comment" choice, but rather a revised wording on the delete button (like "delete with no comment" if no radio button is selected).
Sorry for the messy mouse writing ;) I know this is a small change but I figured since this just showed up it smaller suggestions wouldn't be so bad.
Radio buttons can't be unselected; it doesn't make sense to have "unselected" mean something. I really think this should remain as an explicit option. Just because I pick one of the other options doesn't mean I should never be able to pick the no comment option; that's effectively what a "no radio selection" implementation would mean.
Changing the delete button's text is also dangerous; at a glance it could seem the only option is delete with no comment, since that's how the button appears by default. It appears to make the form meaningless, then suddenly changes if you select something.