It really, really is not. A sniper is sent to places where there are known or suspected enemies, his orders coming from a chain of command and only allowed to shoot in that specific instance, in that specific space, at that specific time and often, specific people that are pre-approved.
That depends. Sometimes there's a specific 'kill list' (which may be just one name), sometimes there's a 'kill category', depending on the situation, and it can be very broad. For ex, a sniper behind enemy lines doing commando work might be told 'Use your own discretion' and anybody counts as long as its an enemy.
Or a witness. What do you think a sniper in wartime, behind enemy lines, or in some similar situation, does when he gets spotted by a kid or an innocent bystander or whatever? Somebody who might tell the enemy about him? Might give away the entire operation?
And of course, when a sniper is operating unsupervised, even if he has specific orders, it's more or less a matter of faith whether he follows them.
The Blackstaff has no orders. He has no real oversight. He has full discretion to do whatever he wants (remember, "What's the point of having a license to ignore the Senior Council if I don't use it?"). He is not sent after a target -- he decides who to kill, when to kill, how to kill, and can do so whenever he wants to.
In theory, maybe. In practice, the Blackstaff has to consider the consequences of his decisions like everybody else. He's still just one man, honk off enough powerful people and sooner or later it's going to catch up with him. The Council outnumbers him thousands to one, and could wipe him if they wanted to. Or if gets
too carried away, they could refuse to back him up. Or they could physical take the blackstaff itself away from him.
Or they could pick him off with a sniper rifle. Or poison him. Or whatever. He's still just one man.
I still find it hard to believe the majority of the White Council is unaware of the Blackstaff. It's been around for a very long time, and wizards instinctively are curious, and gather knowledge. It's their nature. They also seem to associate with the supernatural community, again sources of information on the Blackstaff.
I doubt they know the details. I don't think most of the outsider supernatural community knows the details, Kincaid is probably an exception there. But it's pretty likely that both the general Council members and the larger supernatural community (at least the major players, not necessarily people like Anna or the like) know that
something exists, and have heard rumors or have their suspicions, even if they don't know the details.
I think it's more likely that Harry personally didn't know for a number of reasons.
1. He's young for a wizard
2. He has been shunned by the Council, and seen a a security risk
3. Harry avoids the White Council
I think the 3rd reason is the biggest. Harry has gone out of his way to avoid everything to do with the White Council and only exposes himself to them when he has no choice. I think most wizard folk who are involved with the Council probably know of, or at least heard whispers of the Blackstaff. I doubt that they are 100% unaware. It's more likely that they suspect, but can't confirm.
This^^^. Harry, at least at the time that he found out about the Blackstaff position, had been making a point of avoiding the rest of the Council for the most part.
Both Maggie Sr. and Harry were and are members of the White Council. I.e., the White Council has outright told him to take out its own members.
Yep. That's a big part of his job. To take down the warlocks that are so badass, so powerful, or so whatever that the Wardens can't handle them on their own. That's not his only job, but it's a big chunk of it.