User blog comment:Ḡwẵine Ḹٍٍkƨ Ĺiĸe Ͼềлȑềd/Series 5 will be the last! - unless we act now!/@comment-4916403-20120909122943/@comment-5102537-20120909140324

This one could be added:

Arthur suddenly knowing about his birth after he wanted to kill his father in season two because of it and what he now obviously accepts just so and what has been the second most important secret after Merlin's magic throughout the entire show for at least 26 years.

As for Isolde, I hated that she died. Tristan and Isolde were a real interesting pair. But I'm not sure that Merlin could have healed her when everyone was standing/sitting around. She died seconds after he arrived.