I would think if you had another IP address and email you could re-register. I don’t think you could do this from the same computer you had while posting under your old account. ???
Correct. While people can change their IP address with VPN; their physical MAC address that connects a given device to the Internet does not change.
https://whatismyipaddress.com/mac-address
Using a different device and VPN or just a requested change in IP address by the IP provider would allow someone to register as someone new using a different username.
Both easy. DHCP and Gmail.