Comment 3 for bug 1136343

So, the above comment really applied to protocol 1.
We're really only interested in protocol 2.
I've walked through the sshd code, and the relevant code here is:
 auth2-pubkey.c:user_key_allowed2

It basically does:
 - parse the line, ignoring the possibility of options entirely
    if that is a valid key with a valid key type, then use it
 - otherwise remove comment from the beginning and try parsing again
   - if that succeeds, use comment and key.

list of known types in (key_type_from_name in key.c):
 - rsa
 - dsa
 - ssh-rsa
 - ssh-dss
 - ecdsa
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