Nope. Sombra is gone. I mean, that character was good for like two episodes but I'm not sure I would want to see more of it. I don't think it stands the comparison with Discord.
Dragon Ball, Dragon Ball Z, Breaking Bad, The IT Crowd, Homeland, Game of Thrones, MLP FiM, Banshee...
They're also lots of TV shows I started but never finished - or some that I'm still watching.
I also prefer to call myself a fan than a 'brony'. I don't see why this community would require a specific label. I do however accept the idea of people using this term to qualify themselves but I don't feel like using it to qualify myself.
Favorite? Well, I'm not sure it makes sense to talk about favorites. I just use them according to the conventions depending on what I'm doing. The post above sums it up quite well.
Even though it would make some sense, I don't think it's possible. Daring Do was introduced later in the show and is only appearing in a few episodes. It wouldn't really fit the storyline.