My conclusion?

1. Then it turned out the purple flowers were called poison kisses, and Arya got a rash on her arms. Sansa would have thought that might have taught her a lesson, but Arya laughed about it, and the next day she rubbed mud all over her arms like some ignorant bog woman just because her friend Mycah told her it would stop the itching. (Game of Thrones)

2. They spoke of a one-eyed man and another who wore a yellow cloak . . . and a woman, cloaked and hooded.”

“A woman?” He would have thought that the White Fawn would have taught Merrett to stay clear of outlaw wenches. (Game of Thrones)

Hi. In example 1, we can say "might have taught" and "might teach" interchangeably whereas in example 2, we should stick to "would have taught".

I think I can reach such a conclusion: unless two or more past events are referred to, which makes perfect modal mandatory, we can very frequently use plain modal and perfect modal interchangeably with the same meaning after "would have thought/had thought/thought" to refer to a past event, be it one-off or durative.

Do you endorse my conclusion?

Thank you.