Mail.app signature has extra spaces before text

I've had an odd behavior pop up in Mail recently. When I compose a message, until a few days ago, Mail would create a new message with one carriage return (as it were), and then put the signature (as desired).

Now it seems that Mail has decided to issue two carriage returns before the signature text, so that there are two lines (blank) in all new messages. Mostly for aesthetic reasons, I prefer the old behavior, but I can't seem to figure out how to change Mail's default message template.

It seems that this behavior only occurs when I have a signature to add onto the end of a message by default.

I've tried altering this via the customize... menu, but the changes in the message body text don't seem to take.

 

Nope, no attachments. Just the text of the message.