Using almost anything but : would have been fine. Could have used 2001~1001~~1 instead of 2001:1001::1, which looks weird today, but wouldn't have done if that

Using almost anything but : would have been fine. Could have used 2001~1001~~1 instead of 2001:1001::1, which looks weird today, but wouldn't have done if that had been chosen all those years ago. (unless : as an ipv6 separator predates its use as a separator for tcp/udp ports, in which case tcp/udp should have used ~. Other symbols are available)