Well there's something seriously messed up. If I uncomment the NickServAlias line AND comment out the inclusion of the anope aliases in unrealircd config, the errors become less frequent (though the reasoning behind it is still unclear to me).
MySQL seems to act even weirder, tried to optimize the anope_ns_alias table through phpmyadmin and now I get one line of NickServ collision and seven lines of ChanServ collision as a new bonus. It's still good to know the origin of the problem lies there, will give it some further testing when there are fewer annoyed users
edit: after optimizing the anope_cs_core table (hope it was this one, some cs for sure), the ratio of NickServ and ChanServ collision errors is 50:50, aka 4 and 4.
[Edited on 6-8-2006 by Robin]