There was a going theory that the W was actually an M being placed by Morgan. But after this week I kind of doubt that.
I don’t see Morgan tying a woman to the tree to be fed on by walkers. Morgan would have also had to follow the group all the way from Georgia to Alexandria.
I doubted it right off the bat, why the heck would he carve an upside down “M?” That’s just kind of a lame theory.