When was this changed? Was it changed at all, or was it this way all the time?
Good thing you rememberd to mention, because of what speedball said, god knows when most of us would catch on to that. If you hapen to figure out why we haven't figured more such stuff out by now, do tell us these things

EDIT, QUESTION:
Also, does this mean that one level of corrosion on all AA's in a level COULD make Pissorf take out one DP each if I slam two 1 HP AA's into one another?