<br><input type="checkbox" name="signature" value="yes" $signaturechecked> <b>Show Signature:</b> include your profile signature. Only registered users may have signatures.
In newreply and newthread templates, change to
Code:
<br><input type="checkbox" name="signature" value="yes" checked> <b>Show Signature:</b> include your profile signature. Only registered users may have signatures.