I think Alma Jr. and Cassie were speaking in code, as it was and is necessary to do in Wyoming. "He's not the marrying kind" as you pointed out, is code for gay, and "You don't say much, but you get your point across" means "message received." Still, I think Cassie denies the reality due to Ennis's manliness and virility.
That's exactly what I was wondering when I asked about this at the beginning of this thread years on years ago. Is that what they were "really" saying? Or is it what we, the audience, are meant to wonder about? Either in an ironic way, because we know it has a double meaning in this case, or in a confused way because we don't know if they actually meant that, or if they were just saying, "He doesn't want to settle down." "OK, I get it."
I think Diana and Larry intended both meanings, deliberately ambiguously. By choosing phrases that fit both a superficial interpretation and the double-meaning interpretation, they were letting us share the feeling that Jack and especially Ennis lived with all the time: What do the people on the pavement suspect? Are the pool hall guys about to jump me? They can never be sure. The movie uses this technique on and off throughout. (Recall that the bartender also uses an ambiguous phrase!)
On another topic, Lee, I'm saddened and surprised to see you put it in present tense (was and is). Granted, I live in a bubble, but from what I've seen I feel like people these days are far less homophobic now than they were even when this thread began. Now that marriage equality is the law of the land, now that lots more movie and TV characters are gay without it being a big deal, they've kind of acquiesced to it. Plus, bigots can turn to another target -- now they can be transphobic!
But I don't live in or near Wyoming, so maybe it hasn't changed as much there.