On the first point I see how Sera is divisive. She is one of two gay characters in the game. I can see how lesbian players might feel a bit irritated with her portrayal. It might have gone down differently if she had followed a gay Cassandra type. Still I would think this is not what the writers intended. I just doubt they meant to cause any hurt or offense. Sometimes people just don't see all the consequences through in their planning stage. I still think Sera is a good character and she isn't a bad person and I firmly believe we have not seen the last of her. I think we'll get a chance to see her evolve.
On the second point: Yeah. I've seen that and it makes no sense to me. It's a game. These characters do not really exist but people get way too passionate about them to the point they lose perspective. But fandom is like that. I remember in the 80's in Junior High two guys I hung out with getting really snarly with each other about who was cooler: Kirk or Spock? Nonsensical, right? It's a silly thing to start tossing expletives at someone over but people will do it. Yeah guess we didn't need the internet to get that sort of thing going!
As I've said, I like Sera a lot. I'm not disappointed by her because she's a bad character or person. I'm not disappointed by her. Again, I like her, and I do look forward for more content involving her in the future.
I'm just disappointed by the fact that considering all the history about troubling lgbt representation in media, they gave us as a first lesbian companion someone who was made to be divisive on purpose; I mean, she even has the option of being kicked out at any time in order to give people who dislike her a way to get rid of her (which is something I don't get, it's like they assumed that, amongst all the companions, only Sera would have been so disliked that she needed a "kick me out" option at any given time).
Should Sera have never existed? Hell no, I'm glad they wrote her. Should Sera have not been the very first lesbian companion in the franchise? Eh, it couldn't have hurt to have a lady knight in shining armour who happens to be gay instead, for once.