GPG 1.4 and 2.6-style keys

[Robert J. Hansen]

For reasons I've never quite been able to figure out, some people are  
fond of their legacy PGP 2.6 keys and are reluctant to part with  
them.  Nowadays I'm getting some traffic from people using legacy  
keys with SHA2 as a signature algorithm, which GnuPG 1.4 sees as a  
signature conflict.  Is this new behavior to GnuPG?  I don't recall  
seeing signature conflicts of that sort in past releases.