Marvel gets to decide what's on topic for Marvel, trashmeme gets to decide what's on topic for trashmeme.
Which is to say: the "no dark good guys" rule isn't a statement about the general acceptability of mirrorverses or dark AUs, it's a broad guideline about the kind of badwrong this meme is geared towards. It's open to revision if the new Hydra!Cap material is trashy enough to shift people's interests. But overheated Tumblr rhetoric for or against isn't a terribly good indicator of fandom's interest in creating stuff, so we'll have to wait and see how it all shakes out.
Re: hydra!steve?
Which is to say: the "no dark good guys" rule isn't a statement about the general acceptability of mirrorverses or dark AUs, it's a broad guideline about the kind of badwrong this meme is geared towards. It's open to revision if the new Hydra!Cap material is trashy enough to shift people's interests. But overheated Tumblr rhetoric for or against isn't a terribly good indicator of fandom's interest in creating stuff, so we'll have to wait and see how it all shakes out.