Haha it really was Edlund to the rescue in 6x22 right? Sera getting her hate on (she was very bro-centric) but Edlund was not about to let that fly. Thank Chuck he was as good as he was, not just in writing Cas and working with Misha but just storytelling in general. You FEEL the love and care for Cas in his writing. And there's a general weirdness and dark comedy running through his episodes that I love.

I don’t think Sera was hateful in any way - I think she just didn’t get or care about Cas a whole deal… I mean she let Edlund pitch 6x20 and take up valuable time to tell an episode which actually moved the plot on roughly five-ten minutes of plot content from the reveal at the end of 6x19 with the drama that could have happened, say if you only saw the Dean, Sam and Bobby POV stuff from the episode :P So she had to appreciate what others had to say about him, just not finding very much to say about him herself, or for it to occur to her that his side of the story was worth telling or could be made compelling or interesting.

There’s a quote from her which says Cas has no subtext and I think she generally just didn’t look too deeply into Cas and saw him just as playing piece on the board left over from the apocalypse arc - important to the plot in his own way, but emotionally expendable and not particularly worth any exploration beyond what he could do for the plot.

I mean, the indifference is sort of almost worse than hate, when it comes to satisfying storytelling (when I was writing rewatch notes for 7x21 vs 7x23 I talked for like 10 paragraphs per every line Cas said in one, and then vaguely summarised a scene with Cas in it in the other >.>) but I don’t think anything she did was intended to be cruel.