I didnīt bother to read all 41 pages so maybe that was already mentioned...
I stumbled upon a problem with obsidian walls: I cheated some magma onto my map (using the newest version of DFHack for 0.34.02) and then used a screw pump to pump it over a water basin. The water directly below the pumpīs output became an obsidian wall, naturally. Currently it looks like this:
(cross section of 3 z levels)
FPPF
OWM
WWW
F=open space
O=obsidian wall
M=magma
W=wall/floor
Now I have the problem that I canīt dig out the obsidian wall (set destination to mine, but none of my dwarves goes there and actually digs it out) and I also canīt operate the pump anymore (dwarf goes there and starts to pump, but no magma flow - I would expect the magma being pumped onto the obsidian floor, but that doesnīt happen).
It looks like part of the game (responsible for showing the map) knows about the new obsidian wall, and another part of the game (responsible for handling interaction like magma flow and dig operations) doesnīt know about the wall... just like after digging on a revealed map then unrevealing it afterwards the dug out sections need to be discovered by dwarves again (by digging near them).