Doesn’t get you their mana. It should. -/- counters also don’t generate the mana.
-/- counters should not generate mana if when the creature dies has 0 attack cause of the malus.
If instead it had still some attack(like a 5/2 scion dead cause of -2/-2) then it is most likely a bug.
Replacing do not trigger any “on death” effect.
This is by design.
Of course it’s the ‘equal to power’. Which was 0. Thanks. I should read cards properly.