I installed Hammer on my sister's laptop for the time I'm going to stay here, all went well and such, but when I tried to make a map, I noticed in the 3D view something strange.
My brushes had vertices diagonally too, as if they were clipped. I pushed the clipping tool button to see if it actualy automatically clip the brush. Nope.
I used then the Vertex Manipulation. This affected those "phantom: vertices when I moved the vertices points.
Here are some screenshots : And I suspect this weird behaving to be the cause of an error I get, one I never got, something about "readsurf".