I was mining near the village's wall, and a coal vein popped up, spreading blocks around like it does. I picked up a piece of coal that I mined NOT on the wall, and it destroyed some terrain. Sorry about that!

When placing flooring down, if it overlaps any other object that has already been placed down it will make it disappear and you can walk in that space as if the object wasn't even there (except for teleporters and the function floor)

If you're mining and you right click half way through to sell something underneath you, it cancels the mining.

I'm holding a direction to mine then using my mouse to sell simultaneously. Works well for clearing up dirt left behind. But if you right click while mining it'll cancel the mining, and if you're holding the direction to mine you'll have to repress the direction before it starts mining again sometimes.