TBH it's silly that IRC clients and servers still respect the 512-byte limit for messages. Clients should send a command (e.g. something like PROTOCTL NOMSGLMT) to let the server know it supports messages of arbitrary length. And the server should cut off messages as before for every client that hasn't sent the command in question. Or there could be a limit matching the limit in the Matrix protocol if there is a limit in e.g. Matrix.

Seriously, I think message length limits are the main thing that's holding back the IRC protocol. If you can send e.g. 65536 byte messages, anybody will be immediately able to create scripts for sending images or code snippets.