Make sure you mention that you are going "AFK" or "BRB" in Party/Channel chat so that other members of the party will know.
People might think you are leeching (not contributing to the party, but gets all rewards/loot/exp/gold) so they vote kick, because the player in question may have failed to state in chat that they are going AFK for a minute or so to do something in real life.
But yes, quick leaving at the end of the battle that people think is really smart is in fact really dumb and should be bannable.
-Not playing the game as intended.
-Griefs other players into sometimes leaving them in a glitched state where they are unable to get their drops.
Adding to this, you also lose -1 daily Battle Limit. Let's say it's a raid, you will have to wait until tomorrow's reset unless you have VIP.
Your equipment loses durability as well.
No EXP, No Loot, No Gold
The "glitched state" usually a black screen when the system is trying to connect you to a new host.
- You might be unable to /leave
- You can't get loot
- You can't do anything except return to the main screen and re-join the game again
Some hosts actually do this to troll or grief other players of the community.
Especially on WEST I know some trolls that have multiple lvl 90s and do this.
Just leave the party before the host has the chance to leave.
When boss dies, type in chat: /leave
This will bring up ending screen, you get rewards/loot and all you have to do afterwards is hit that "Return to Town" button.
Usually what I do.