WinVN in particular and threaded news readers in general have always had a problem with fragmentation of the newsrc file. Since the newsrc file keeps track of "seen" articles as a list of ranges (ie: 1-4,6,10-12,etc..) this leads to a compact storage of "seen articles" only if you display your articles sorted by article number. If you sort via threads (the default way most people use WinVN), then the list of ranges can quickly get into the 100's. Marking of crossposted articles only increases this fragmentation problem. This is why crossposting of non-subscribed groups is an option.