For the record, my issue with the trope is not quite the same one you're describing.
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My issue is not with Q's death specifically, but the end of Quelliot. The show has plenty of diversity and representation in the characters; they're superb at that. (Plus, I suspect about half of the characters are at the very least bi-curious.)But in a show that feels chock-a-block with different relationships, the Quelliot ship was the only one I can think of among major characters that was not the 'default' of a heterosexual relationship between two people. So this still feels a little like the 'kill your gays' trope, just with a relationship instead of a character.
I know that's not what they were going for. And narratively, killing off Q made sense. The death was handled incredibly well, both in the writing and execution of the episode, and everything leading up to it this season. All of that is why I'm just a little upset/annoyed over this particular aspect of it, rather than actually angry in any meaningful manner.
But the problem, as always, is that if you have a cast or story dominated by one particular thing (mostly white folks, mostly dudes, etc.) then the one odd-thing-out ends up becoming a proxy for that entire class of thing. If you have a show that has a cast that's, say, 8 guys and 1 woman, then if you kill off that woman it ends up coming across way worse than if the show had 6 guys and 4 women and you killed one of the women off. If you have a cast that has 7 white folks and 1 black guy, then if you kill off that one black guy it comes across way worse than it might otherwise. Etc.
And if you only have one relationship on the entire show that's anything other than what people think of as the 'default', then if you torpedo that one relationship it's likely going to come across worse than you probably intended.
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The show is about wizards who have relationships and do dangerous things that are life threatening, and not about representing social tropes based on every single viewer's personally declared or undeclared race, gender, or preference.
Besides, for all the Quelliot love, Q had just gotten back together with Alice after being shot down by Q in a flashback.
This is exhausting.
I loved Quelliot and would have preferred to see the two together story-wise, but that they had their orchard and a lifetime together was beautiful, making the death more tragic and the moment he dropped the peach in the fire all the more impactful.
It's about wizards. Not about you, and if anything from Star Wars to Marvel to whatever is going to survive, fandom needs to get off of this obsession with every last thing being representation>story.