Compatibility to RFC 1583 is necessary when you use older OSPF routers in your network which do not support the current standard RFC 2328 but just a prerelease draft standard RFC 1583.

Because the Compatibility feature doesn't harm or hamper OSPF acc. to RFC 2328 this Compatibility is activated by default at Hirschmann Platform 5 devices. Nevertheless using only up-to-date routers you can de-activate this feature without any doubts.