should work but this looks expensive, I wonder if you can do the opposite: iterating over thread-bound drafts, find if there is an element, and update that thread if yes. I don't know if we can do such iteration though, but this would give the following improvements:
* we don't need to call "thread.hasDrafts" since we're already iterating over drafts. And "hasDrafts" looks somewhat expensive
* we don't need to iterate over all threads that are already displayed

If we can't iterate like this I propose now, then let's keep it like this, as the odds are that there won't be much threads already displayed when we get the drafts request callback. But if we already can, or if it's easy to add, I'd much prefer to do it like this.