As long as I remember, mentioning a server was totally okay. We didn't warn, we didn't ban.
Advertising and mentioning were considered two different things. I guess times have changed then.
I can't really imagine "losing" people due to any of those two mentioned anyways.
If you mention a server, everyone knows, people can relate.
If you deliberately advertise a server, it only annoys people most of the time.
Warning someone for mentioning giants like HP, SB etc. etc., seems just like a Helper doing his "job properly".