For example, can he stand anywhere as long as it's not on opponent's court? Or even sits down on the court? Can he runs around while his partner is being served?
Technically, the receiver's partner must not block the server's view of the receiver. In practice, unless you bring a fat giant player with Akane Yamaguchi behind him, this is not feasible, and even then, the tactical advantage would be negative. Other than that, of course the receiver's partner must not try to distract the server: Per §16.5.2 all players must be on court; the receiver's partner is not allowed go to the bathroom and let the receiver play singles for a while. In summary, there are a bunch of theoretical rules touching this, but in practice, the receiver's partner can be anywhere on court, sitting, running around, or whatever – unless their antics are designed to distract the server.
To add to what @phihag said, the way I understand it, the term "unsight" mostly goes for not been able to see the shuttle and the racket of the server. So even if Yamaguchi stays in front of Kolding, it would not be allowed for her to block the view of the shuttle...
TBH got faulted for moving even though he wasn't the receiver. Is this normal? Seems very strange to me.
That was a classic one! I was laughing a lot about it.. Completely incorrect call, yes. An example, when players should have asked for the referee - "point of law" and not "point of view" of the umpire
No, this is very clearly not a fault at all. Note that this is one of the few cases where players should actually call the referee, because they can appeal to the referee on a rule of law.
