Comment 43 for bug 615300

I, for one, fail to see a problem here as long as it's simply a pre-set signature which is seen while typing an email and can be deleted both once as I'm typing a message AND deleted for good from the signatures. Just make sure the signature is below a double-dash so mail clients interpret it as such, and, to prevent accusations of copying aPple, do it like Opera's mail client does it:
====== signature starts here ===========

--
Using Opera's revolutionary e-mail client: http://www.opera.com/mail/
====== signature ends here ============
I think "Using Evolution on Ubuntu: http://ubuntu.com/" would work.
Notice, aside from the double-dash, a new mail message has 4 empty lines above the signature, so the signature is sufficiently offset from the body (and honestly, if you can't figure out you're done with a message when you're at "Best regards" or similar, you're not paying attention).