Several discussions at SL show that not everybody understands thickness as "a wall facing open area, technically not a 100% alive but almost invulnerable". It has been my own understanding of the concept, but apparently thickness is something else. It's the abscence of defects altogether and neither the position being a wall nor its facing open area seems to be relevant.

The page I have written about thickness should be rewritten and your writings painfully remind me of that. Dieter