I'm sorry, but you speak of a lack intentional writing for what the writer implies, and later in the post claim that there was an unspoken promise between you and Mizz. You cannot have your cake and eat it, too. Mizz and Bromm have had time to develop a relationship like that since before you joined the crew, and you cannot expect him to suddenly go monogamous with someone who just showed up and is *starting* to develop feelings for. That is a selfish and short-sighted reading.
Sorry, we're here continuing a discussion that was started a year ago, you're out of the loop and just haven't seen that I've addressed this before.
I'm not asking to change anything, just add a couple of lines - Mizz acknowledging that he is not offering an exclusive relationship to Rael and he's messing around with someone else would be fine(other characters give you a fair warning, there's no reason why Mizz shouldn't).
The problem isn't that Mizz is polyamorous/polygamous/whatever, the problem is that not mentioning that little fact while coming on to Rael comes off as manipulative and insincere, which was not author's intent, as far as I can tell.
They are just being intentionally dense about how poorly that part had turned out, readily accepting praise, but ignoring criticism. I like their writing, but I'm massively disappointed in them as a person.