I do love it that y'all make me think about the why's of the ways I think.
For me, "queer" is about the attraction/behavior factor. I guess I see anything outside the norm as being queer so, yes, I know heterosexual people who are queer and I know gay people who are not queer. That's partially me slapping my own label on people and partially the label they choose for themselves.
I think being butch/femme/trans is not, in and of itself queer as much as our attraction to others outside the "normal" spectrum of what is expected somehow queers us. I have many friends who are female ID'd lesbians attracted to other female ID'd lesbians. They do not ID as butch or femme. This is kind of the normal, expected version of lesbian relationships so I don't really see them as queer and most of them don't see themselves that way and many of them are horrified at the word. On the other hand, I know a ton of people who ID as heterosexual but have attractions to / interactions with people in very queer ways.
I think, for me, "queer" is in many ways tied to kink so, based on my reference points, anything that may be seen as "kinky" to the outside world would be seen as "queer" to me. This would include not only people involved in specific BDSM activities but anything else that is viewed as outside the norm for those individuals.
As to some of Dylan's questions, I know several women who are married to cismen and ID as heterosexual who hang out on b-f websites and a couple who hang out in b-f and/or primarily gay kink space in real time. The specific circumstances of their relationships are not my business but if this is where they feel comfortable and what they consider their community, I'm not one to tell them the don't "belong" based on their current relationship. For me, this would go back to the part about individual ID's not being based on who someone is partnered with.
Personally, it would feel a little icky for someone who ID's as a heterosexual male, and does not see themselves as queer in any way, to be here for the purpose of meeting a potential partner (whether that's for a relationship, dating or sex.)
I tried to think this out but I doubt I did a very good job of it really. So, I reserve the right to come back later and completely contradict myself if questioned!