Steve is worried about Comodo for security. Leo says that Comodo is not Kommodia, so it's not a security issue like Kommodia is. Superfish uses Kommodia to get beyond web browser security, but it was even worse. Comodo, though, is a completely different software. SSL certificates can be circumvented by those who visit Steve's site and there really isn't anything he can do about it. It doesn't really affect you -- it affects them. So Steve should get the encryption he can and understand that it's possible the end user will get something that breaks it on their end, not his.
Leo likes DigiCert, though.