Mailing list duplicate-elimination question

Although I have all my PG mail list subscriptions set to "unique"
(send only one copy of cross-posted messages), I've been noticing lately
that that feature doesn't seem to work as well as it used to. I've
gotten a fair number of multiple copies of cross-posted messages.

I did "show tgl@sss.pgh.pa.us" in majordomo to verify that I had all
the lists set to "unique" mode, and it seemed I did ... but I noticed
that it shows
Subscribed as Tom Lane <tgl@sss.pgh.pa.us>
for some lists and
Subscribed as tgl@sss.pgh.pa.us
for others. Do you happen to know if that might bollix up the
duplicate-elimination logic?

regards, tom lane