As Reputation grows beyond $NORM, the effects of a downvote are minimized.
i think you are right here... i would expect that "younger" monks are more concerned with -- on their posts because it has a much greater impact on their XP... it can be frustrating to feel like your really beginning to be a part of PM, and then get down voted on a post that is many months old...
it can feel like being punished for past mistakes...
i just got downvoted for reply on my first post four months ago, when i still didn't have any idea how PM even worked... but i lost four XP because of it... this i think is the downside to no downvoting aging: past posts that weren't great get worse...
maybe then i'll have to start all my nodes with: The Scarlet --
having said that, though, i do agree that it doesn't happen enough, or has enough value, to warrent revising the XP system...