I exclusively use Apple's iMessage for chat. Most of my coworkers use Adium. Ever since I started this job there have been weird issues were coworkers can't see me online and don't respond when I message them. I've confirmed that they are not actually getting the messages (and they aren't quietly hellbanning me).
Also, the name of my lapop is the Emoji characters 🐒💨.
Also, your default location in iMessage is the name of your computer.
Turns out there's a bug in either iMessage, Google Chat or Adium (probably Adium, since iMessage <-> Google Chat works just fine) where Emoji characters in your location cause you to not be visible in Adium. I changed my location to something more vanilla and now all my coworkers can see me online. Hooray!