This is a userscript that requires either Greasemonkey for Firefox, or Tampermonkey for Chrome. I imagine it will work in other contexts as well, but those are the only two userscript plugins I've tested it with.
There's no preferences/settings available yet, but if you want to turn a particular feature off, you can edit the script and comment out the appropriate line in the processNewMessages() function. (e.g. put a //
in front of highlightUsername(newMessage);
to turn off username highlighting.)
Feel free to submit questions, issues, suggestions, pull requests, etc. to this Git repo.