Seth obviously remembers, but Sekhmet told him how she had been the one behind it, so... Seth knows Horus wasn't the one to blame (and moreover, I'd figure he'd readily accept it wasn't Horus's fault since Horus is still "human-ish" and he wouldn't want to think a "human" was the one who successeded in harming him).
Argh true, this is so frustrating and sad. Nepthys should’ve just not made that deal with Osiris in the first place, Anubis suffered, being Osiris’ puppet as you said, feeling like Seth hates him :(. And Seth suffered as well, humiliated by Osiris (raped; Seth’s pride), and being misunderstood so much, etc.
I just have to hope for S2 to be better compared to S1 which was plot focused of course.
so does seth remember what the possessed horus did to him (rape)? Ack.