Tested in 1.42-B, but Wafflem's avatar suggests that it's still in the current version. <_<
The pin (effective coordinate) of an L1 and NL lemming is inside the floor. The lemming's white foot is above the floor. Therefore, the pin is 1 pixel below the white foot.
The NL editor allows preplaced lemmings. Preplaceds have a special sprite in the editor: A still walker frame, and a red dot. The red dot is on the same height as the foot. When you run the level, a lemming appears with its pin exactly where the red dot was. We see how the red dot marks the pin correctly.
When you insert a preplaced, you must move its foot into the terrain. Only then will the dot be at the correct position. The ingame lemming will have its foot above the terrain.
Expected instead: The sprite should be shifted upwards by 1 pixel in relation to the dot. The dot stays where it is.
-- Simon
Some newer graphic sets have already fixed this issue (eg. the LPIV / LPV ones). Even more so, the experimental version no longer considers preplaced lemming an object type, but rather, a seperate gadget altogether. Making modified graphic sets / making an update to current versions would probably break more than it'd fix (or require some kind of backwards-compatibility coding); since the new version already requires (and has) BC code and require re-testing / possibly touching up inherently as a result of how many changes, it's better left for that.
Yeah, resolve this along with the set migration.
-- Simon