Leaving and Rejoining Automatically

[Collateral]

Now before I post in the reports section I wanted to check if it's a common/allowed thing. I've seen a couple of players that automatically leave once their health drops to a certain level, they are also able to rejoin after been kicked. Now I'm assuming that the rejoining part is a glitch, but when someone leaves in less than 5 seconds and automatically once there health drops, makes me think something might not be right haha. So if someone can clarify this for me, because it's bloody annoying.