I really appreciated how the bisexuality was just there without being joke fodder or plot conflict.

I was wondering the same thing. The first question under 'stray observations', if answered, could be a major spoiler.

F - This was the worst episode I can remember seeing. The writing and storytelling was so lazy, it's almost as if the story was put together from bits discarded from other episodes. Even in the Whovian universe, this story made no sense.

Exactly … that's what I heard and took it to be.