This post is chalk full of misinformation!
WOW
First of all, This all started when Reddit, shutdown r/pizzagate after someone with a gun went inside of Comet Ping-Pong ( a pizza shop caught up in a lot drama stemming from a fake news article about Hillary and Co running a child pronography ring in the basement), fired a round, and refused to leave until he was certain there were no children being harmed.
The shutdown of r/pizzagate, a sub-reddit mainly consisting of believers in pizzagate and seemingly propagating violence, caused members from r/TheDonald (another seemingly problematic subreddit) to, en masse, create hundreds, maybe thousands of posts full of hate speech and obscenities specifically targeted at Reddit CEO, Steve Huffman.
Steve, in retalition, went into the reddit database, and changed all instances of his name in these posts, with "r/thedonald". essentially redirecting all of the hate speech back to the perpetrators as a group. He didnt change anything to any single persons name as you stated, but to an entire subreddits name.
He trolled the trolls essentially

I think its genius. Not exactly ethical, but its trolls. who wouldnt take the opportunity to troll a massive group of trolls like that?????????