I haven't tried to exploit mustard gas in LIVAN or CVS, and killing petrus peacefully has apparently become a
more involved process now that 0.50.5 blames the player if they throw a gas grenade at or near a peaceful NPC.
One task which is still trivial is killing the dungeon shopkeeper, Merka.
Step 1: Sell him a gas grenade on a tile adjacent to him.
Step 2: Sell him stuff until he runs out of money.
Step 3: Buy any glassware you don't want broken.
Step 4: Buy and sell junk to train your charisma?
Step 5: Leave.
Step 6. Make sure Silva is happy, make sure you're not on fire, and pray to her.
Step 7. Wait for the gas to clear.
You now have all the junk you sold him, all his equipment, all his money, and all his stock, and a few more points of charisma.
I'm not sure whether I'd consider this a bug, or just an occupational hazard. A possible fix would be to blame item destruction caused by Silva on the player (as Legifer's explosions currently are?). However, that might make Silva's earthquake anger the shopkeeper just because of his lanterns being destroyed...