I don't give a flying fart who you ship together in this fandom.
I just felt the need to say that.
With the following exceptions:
You should not remove parts of a character you don’t like in order for them to better fit your [crack] ship. (Obviously you have your right to do what you want regardless, but it’s just a shitty thing to do in my opinion.)
Ex. If you want to ship Alec and Jace together. Go for it. (I ship them too. Platonically, mostly, but I do. They have a lovely relationship.) I would never make Jace gay just to put him with Alec, because that would be removing his heterosexuality. Just as I wouldn’t make Alec straight to better fit him with a female I think he would look aesthetically pleasing with or whatever. That would be erasing his canonical homosexuality.
Which I don’t think is cool at all.
However, I don’t see a big issue with making characters who haven’t necessarily had their sexualities clearly defined into whatever appeals to you. If a character flirts with everyone & has only ever been with women, but never stated one way or another what sex they preferred (and if the author hasn’t either) I think it’s fine to ship that character with whoever. (I haven’t read the books in a while so correct me if he is noted as straight only, but if the show wanted to make, Raphael for example, be bisexual; I’d be cool with that.)
All that said. If your ship is part of an endgame couple canonically (Ie. Malec, Sizzy, Clace) and you’d rather see them in different pairings, you have to understand that canonically that won’t happen. It’s your right to ship who you please but don’t go arguing with someone about who a character should really be with, ignoring who they actually end up with, just to justify your ship.
Only time I’m not against this is if the couple are clearly unhealthy for each other and while the book pairs them together they shouldn’t be. (Ex. A couple where one is physically/mentally abusing the other - if you wanna ship the poor dear getting victimised with someone better, then by all means.)
I’m sorry for being rant-y. Just came across someone being a dickwad. I don’t mean to upset anyone with this. Just needed to get it off my chest. If you want to discuss it civilly then feel free. I don’t have the best way with words so if something came off insulting or disrespectful I assure you that’s never my intention. (I probably shouldn’t write rants when I’m pissy. Lol.)