I have always Torched claimed leanto walls.
now that leantos are stronger. I will torch them with more enjoyment.
We plan on implementing a fix. We were hoping to have a better one than the "don't build close to this or that" since spacing a leanto seemed annoying. However, the PVP patch didn't bring the solutions we wanted so it will most likely be something similar. In the meantime. Stop building leanto walls.