So that's what I was originally thinking of but because of the nature of BBCode, you can write a quote without specifying an author, message, or timestamp. And although I could write something that'll checks and ensures that a quote has some link back to the original quote, that's not how it was built to work (my estimate, not a known fact). Adding that additional check may also break our importing tool since all the quotes in SMF does not support this feature right now.

And that's the fun part about working with legacy data and systems.

I think the best way to think about this problem is to break it down to the fundamentals, it's first principles. The core problem is one user is trying to impersonate another user. The issue with quoting is more a symptom of the disease rather than the root cause. So finding a way for users to be unique looking throughout the system would cure the disease but also ensure that the same thing won't happen through another form like forum posts or such.

Again, any help is appreciated but till then I'll keep thinking about this.