Ok I see it now. I tried a slightly different version of that (different way of turning around) but the lemming just wouldn't build into the wall. Thanks for the savestate. Evidently I use a different rom but it still loaded (but it wouldn't run, and the lemmings were blobs).
Another glitch: If a lemming falls, then lands next to a wall and builds on impact, he will get stuck.
Another glitch, but not that useful: When a lemming is assigned a skill while going down a steep slope like the one in Taxing 10 (just like mary poppins), it will take effect at the bottom.
Now this is a glitch: A lemming can go through a blocker (The blocker is completely ignored!) by building/bashing/mining/digging within the same cell. The skill will be performed in the usual place.