any reason why the message http://gcc.gnu.org/ml/fortran/2005-03/msg00282.html was rejected as spam from gcc-patches, yet accepted on the fortran list?
See
http://www.sourceware.org/lists.html#rbl-sucks
which has a discussion of how the spam filters work, and how to get around them.
Possible reasons
1) The address you posted from is subscribed to one mailing list but not the other (perhaps an alternate address is subscribed on the other list).
2) The address you posted from is on the allow list for one mailing list but not allow list of the other.
By the way, I think it is a word of all caps in the subject line which triggers the spam filter, and "PR" is such a word, which is unfortunate. This is just a guess though.
--
Jim Wilson, GNU Tools Support, http://www.SpecifixInc.com