Reddit shadowbanned me multiple times for either absurd or political reasons, but my ISP used to assign dynamic IPv4 addresses, so I could easily create a new account. Then it switched to IPv6 with a static address, and now I can't create new Reddit accounts anymore.
Hopefully you mean a static prefix, a static address would be an abomination from an ISP in IPv6!
Most consumer ISPs regularly rotate the prefix. IPv6 has proper support for that and can keep connections on the old and new prefix alive for a while in parallel.
With IPv4 most ISPs only rotate IPs on new connections (router restart). But my old home internet even stayed on the same ipv4 for years. Only if I shut down the router for a longer time it got a fresh ipv4 assigned.
So it's an implementation detail, not a technical limitation. Not rotating the prefix is a bad implementation.