you can't change the name of your account on blockchain, so they would have to make a new one, then ask everyone to undelegate and ask everyone to delegate to the new account. it is probably just to much complication.
from what i seen in last few weeks they are using some kind of "search" to see are users repost old posts. not really sure how it works.
They can search, but if they are so community thing, why they are downvoting with account with steem name in it :D it just a fun fact. They started new Hive block chain but using steem name. Just saying..