The Watch-whers... I enjoy the Fact that Wind Blossoms creations finally got a little bit more attention in the Dragon's Kin, Fire and Dragon Harper. Since they got next to none in most of the books. They are always described as the "Faithful" Night watch and that is about it.
Their almost extinction at the same time in that Trilogy.
I never remember the mention of them being able to eat thread. I also liked the fact that the characters determined that their eye site wasn't necessarily influenced by light as much as a heat.
With the inverse way the whole world of Pern has been written. It really makes you see the potential loss of information over 2500 years.