There is no official DBO IRC server. However, there is Team Schooly D IRC, home of the Fighting Robots and the official unofficial IRC server of bungie.org and its affiliates.

server: irc.teamschoolyd.org
port: 6667
channel: #tsd
web client

We boast some of the most incredible credentials in the biz:

• Numerous DBO regulars
  
• At least a couple of DBO admins
  
• TSDBot, the IRC bot that has changed the game and the only one with streaming video integration via TSDTV
  
• Video games
  
• Marty O'Donnell stops by sometimes to bug us. Yes, THAT Marty O'Donnell

There will be a lot of Destiny discussion in the chat in the next couple of weeks. If that's what you're looking for you should definitely join!