Today we've enabled login by email address on Branchable, as an alternative to openid login.
So, all you need to make a site on Branchable now is an email address! Also, users can log into your sites on Branchable using their email.
We know that some Branchable users were relying on now defunct openid providers like Google and MyOpenid. We can switch your sites over to use an email address instead if you want; just get in touch.
Yes, if someone can see your email, they can login as you. The login emails do have some safeguards:
This should make it secure enough for casual users editing a wiki or commenting. In some cases, it's not the best choice for logging in as a site's administrator, and you can keep the administrator logins limited to openid if necessary.
Encrypting the login email with gpg is a good idea, but would have to be implemented in ikiwiki ... and you would have to paste in their gpg public key so it knew who to encrypt to.