While looking what the PGP Global Directory is, I have found that it's key has two strange signatures:
pub 2048R/CA57AD7C 2004-12-06 sig dirct 4DD19F10 2014-01-21 __________ __________  sig dirct 0C2F4392 2014-03-15 __________ __________  Fingerprint=50BB 6FFC 9719 DFD2 BEBB 04C6 9710 B89B CA57 AD7C uid PGP Global Directory Verification Key ...
(from Ubuntu keyserver)
Looks like they are direct key signatures (type
0x1F from RFC, section 5.2.1), and as far as I understand, there is no point in them other than self-signature or revocation, but signatures above are neither of them. So, is there any other use case that makes sense, or are the signatures above someone's mistake?