That would close things off for most nodes but there are lots of nodes running on Tor or custom ports. Not to mention other channels like satellites that are us

That would close things off for most nodes but there are lots of nodes running on Tor or custom ports. Not to mention other channels like satellites that are used for transaction distribution. Junk transactions could stop a few nodes but all transactions are verified locally on nodes and won't be broadcast if they turn out to be junk.