Pretty much what the title says, it takes long numbers without commas and adds commas. Enjoy!
https://chrome.google.com/webstore/detail/diablo-3-profile-with-com/lfojjpdgdcfbncgognnalenbeojlbgej

Source is up on GitHub for anyone interested, the actual code is about 20 lines.
https://github.com/drourke/d3-commas/blob/master/main.js