Quote - Which raises an interesting qustion. Why bother with mutti-copy checks over the local net when anybody nowadays, practically without doing anything special, will have a firewall that prevents it from finding other copies?

Agreed.
Just another bit of legacy code from an era when per machine firewalls were practically non-existent that could be pruned.
I suspect that as multiple machines and home networking were also rare at the time, it was aimed more at companies than hobbiests.