static MultiSet<S> allChatLines() {
  new MultiSet<S> set;
  L<File> files = allDataFilesNamed("log.txt");
  for (File f : files) pcall {
    if (f.isFile()) {
      L<S> lines = toLines(f);
      if (isProbableChatLog(lines))
        for (S s : lines)
          set.add(onlyAfter(s, ']').trim());
    }
  }
  ret set;
}