Feedback noted, thanks!
(I assume) terrain height is key for positioning and line of sight, and it's just really not clear given terrain shading, and without a line-of-sight indicator outside of debugging tool.
There is a line of sight indicator outside of the debugging tool, hold C. The terrain right now kinda sucks because there's a lot of small changes in elevation which may block LOS. When I work on the next iteration for terrain generation I'll make sure large parts are completely flat and it's obvious when there's a change in elevation.