Well I haven’t read every post in the thread (there’s a LOT) so take my opinion with a grain of salt I guess.
I just find it unlikely from a story telling perspective that the rumours surrounding Ysonia are accurate, sort of similar to Boo Radley from To Kill a Mockingbird. And maybe I’m wrong, but she really doesn’t seem all too jazzed about being queen?? So that calls her motivations for committing the murder into question imo, especially since she and Alapharen were apparently close friends.
If she did have a hand in the murder, she would probably have had help from her family, and the Maeliahs have been described as rather calculating. I’d like to think they’d be smart enough to do it without pretty much everyone in Ophaesia thinking it was Ysonia. Framing someone else seems like the obvious thing to do, but that didn’t happen here, so yeah. My two cents.