Forest invaders hiding

So here I am waiting to fight in the forest and someone invades me. I find him and he is just standing there for no reason at all, out in the open. I kick him and nothing happens, I then hit him with a fist, but still nothing happens.

A lot of invaders have been doing this and I don't know why, can you shed some light on this conundrum for me? It's really annoying as well because there is one dude I cannot find and it won't let me exit because of him.

Its a way to farm souls, put on the ring and go away for a few hours. the ring keeps summoning you, chanes are another invader will kill the host. so handy souls for doing nothing.

They are hoping for easy souls by you getting killed by another invader.

Ah. I thought it was to irritate the host by not letting them refresh. most of the time I end up finding them and killing them except for the sneaky ones.