It's unfortunate that IDs were not applied across the chans, as they went a long way to solving this issue (a single poster was tagged with a consistent identifier) without compromising the main point of anonymous imageboards (no persistent author identity was attached to messages, post contents stood on their own merits only).

Still possible to subvert, but harder to do so, and it made client-side blocking of particular ids fairly simple.

Tripcodes fail in this regard, as they are elective.