Issue #251I agree with you: The offending destructible tiles should get repainted. You're 100 % correct that any steel-earth-differentiating viewmode would be a workaround.
I've discussed this with geoo in IRC shortly. We considered two solutions: a) all steel gets nubs, or b) all earth may not look grey-and-shiny. We found a) impractical since there are fine-grained steel pieces:
Therefore, all earth should get clearly differentiated from this. Here are the most problematic earth tiles:
matt/bricks/18
matt/bricks/19
matt/bricks/20 (also its upper bars have wrong shading. Light should come from top-left.)
geoo/construction/pillar_32
geoo/construction/pillar_base
geoo/construction/pillar_bottom
geoo/construction/pillar_top
geoo/construction/pillar_top_shaded
geoo/construction/concrete/008
-- Simon