i think everyone here will agree ksing is a real and big problem for such a game.
As xybolt mentionned, if you report and speak about that on forums etc..., you will mostly be heard (at least), and if there is no suite like ban or suspension (and i'm not sure this would be a good solution in fact), at least you'll have a chence to make the practices of player X or Y known so that other players will be aware and "suspicious" regarding these "bad" players...
However, there is a thing i think is important to notice : many ppl shout at "ksing" just because some players come in the room or part of map they are in. Even if they don't take a mob that you started to kill, some players shout immediatly at ksing, but that's not ksing (if i understood the rules...).
Even more, some others claim rooms or mobs just because they were first ont the place. But i don't remember i saw anywhere that it was a "right" for one to claim a room and a "due" for the others to leave a place on demand.
The fact is : there are so many ppl now playing that it is a necessity to share the available resources. Asking, ok, but if it's not "real ksing" then the only good solution seems to invite the other ppl to a party so that every one can get is "part of the cake"...
As mentionned in the last link provided by xybolt (and if my comprehension of the topic is good... frenchies not always have the "light"
What it comes down to is its considered KSing if somebody takes a quest boss from you and you (or your party members) have to finish that quest. All GM events that include quest monsters are free game (the exception to the rule). Named bosses are free game. Stigma and Auizen Ruins mini-bosses are free game. Dragon (and other) chests are free game.
You'll notice the key ingredients in all of these are asking them to stop and reporting the incident. Asking them to stop does NOT mean swearing at them, cussing them out, etc. It means: ASKING them to stop. Reporting the incident means submitting a ticket using the "Contact Us" link. It does not mean PMing a GM or spamming in-game chat.
If i summarize (and simplify a lot perhaps
If you have to finish a quest with some difficult/rare task, there is a chance for ksing being "true" ksing, otherwise, there's a big chance it's nothing else that a pb of sharing (in each other player respect) the place...
In general it's the way i play and nobody (as far as i know) complained "seriously" (even if it's true that some asked for rooms...)
Hope my point of view is correctly exposed.
Wishes to all