can we have a real blacklist plz?

[mosaicex]

It will never happen because it will put too much strain on duty matching algorithm.

Consider the following
Person A blacklisted Person B
Person B blacklisted Person C
Person C blacklisted Person D
...
Person Y blacklisted Person Z
And finally Person Z blacklisted Person A
Coincidentally, they all decided to queue for duty 1. The server then has to check whether the next person has been blacklisted by previous person or not. This could also potentially ended in infinite loop, resulting in duty never popping.
And this is just basic series loop, imagine if Person A blacklisted more than 1 person, and so on.

But I have a solution for you.
It's called using Party Finder.
"But what if I want to do (insert obscure duty here)? It will never fill up!"
And I would tell you that's a realistic result of implementing blacklist in such way that you suggested.