I wonder how many firewalls would break with some of these? I hope they would fail closed (block unexpected traffic). Their stacks probably work on the packet binary data...but the GUI?

The fact that there are still octal-supporting parsers in the wild means that it is a security bug to accept 0-prefixed addresses as decimal, since they will produce a different valid value.

All the other questions are much safer since they will at worst produce a failure, but it would probably be best to be extra-strict for them too.