Digging below the water level doesn't flood or block water. It behaves like vanilla.
Digging under tarpits will make you float like you're in water. Digging near the surface to drain them works like vanilla.
Creatures need a few seconds to learn a fresh tunnel.
Terrain paint is flat, so a cave floor and the surface above it share it. Turn off Underground Painting if that
bothers you.
A tunnel under snow looks like earth a few metres down. A tunnel under a lava flow is a lava tube, and it burns.
MoreTerrainTypes paint is left as you painted it.
Lighting can differ very slightly where a dug zone meets an untouched one, about like any two vanilla zones.
Two players editing the exact same spot at once can briefly see different results. It sorts itself out when the
area reloads.
A dig that crosses a zone border converts both sides, and a dig right beside a west or south border converts the
zone across it.