Validation of User ID with invalid (non UTF-8) encoding

[martijn.list]

Hi,

Some keys stored on the public key servers have User IDs which seem to
be encoded with a different encoding than UTF-8.

For example the key with key ID 0xA8364AC589C44886 shows an invalid
character when viewed online:

http://pgp.mit.edu/pks/lookup?search=0xA8364AC589C44886

gpg is able to validate the User ID

$ gpg --check-sigs 0xA8364AC589C44886
pub   1024D/89C44886 1999-09-30
uid                  Lasse M\xberkedahl Larsen <lml at gr3.dk>
sig!         89C44886 1999-09-30  Lasse M\xberkedahl Larsen <lml at gr3.dk>
sub   2048g/0CA36EF9 1999-09-30
sig!         89C44886 1999-09-30  Lasse M\xberkedahl Larsen <lml at gr3.dk>

My own Java based tool however fails to validate this User ID, i.e., the
calculated hash always returns a different value. Also PGP desktop
reports that the signature is incorrect.

Any idea why this User ID validates correctly with gpg but not with
other tools? Does gpg handle non-UTF-8 encoded User IDs differently?

Kind regards,

Martijn Brinkers