I'm weird about that sort of thing, though - it bothers me when my entire party instantly dies. This probably has to do with the fact that I started playing DM at like 2 or 3 - repressed childhood issues and whatnot.
Looking more closely at the dungeon source it looks like the lightning is done as a set of floor items:
H5906-2 FLOORITEM_LIGHTNING_FLASH 63 3 7 STATE=(INACTIVE) STRENGTH=(150)
(and a bunch more identical except for the coordinates). But I can't find where FLOORITEM_LIGHTNING_FLASH itself is defined due to unfamiliarity with what is stored where in the RTC data files (it's not in DMII.txt).
STRENGTH=(150) would seem to indicate damage when it's activated but could also indicate, say, a light level change.