function processLine(e) {
 var line = e.target;

 switch (line.getAttribute("type")) {
   case "privmsg":
     var sender = line.childNodes[1];
     if (sender.innerHTML.length > 18) sender.innerHTML =
sender.innerHTML.slice(0, 15)+"…";
   break;
 }
}

document.addEventListener("DOMNodeInserted", processLine, true);