And this is exactly why central servers that track everything you do SUCK.
The reality is that this system will degenerate into "anyone who does anything to annoy the mods will be penalized to the full extent of their power". This will be justified under incredibly broad "you agree to do nothing offensive" terms of use clause. And complaining, pointing out flaws, asking questions, and inconveniencing the mods in any way will also be punished. Just like every other moderated system in the history of the internet.
There is no need for this kind of thing either, a better system would be a web of trust style system where you can make friends and your friend's ignore lists are weighted to add to your own.
Instead of a central authority decreeing certain people to be undesirables, it is better to give people tools to help them make that decision for themselves.