It doesn’t actually matter. It literally makes no difference.
Based on the comment they were replying to, “they” is referring to diverse characters in general. This is actually a prime example of how context can help inform the meaning of certain words.
Though for the record, again it doesn’t make a difference to the point they’re trying to communicate.
First is from discussion about character diversity in games…
It’s not hard to understand that they is about “all hypothetical characters that represent minorities and are diverse”…
Here:
First Xanikk said:
then, Valkyr responded with:
and then there was response you quoted!
Second is also plural, but it speaks about Venture’s abilities…
It’s clear from the context of the discussion.
Context do matter…
Because if I say to you “Her backpack is red” is utterly ridiculous sentence (even tho grammatically correct). If you take one sentece out of context like that it’s no wonder you are confused!
Of course context matters, never said it doesn’t, in fact, I said this confusion happens without sufficient context.
In the very example you gave “Someone left a jacket in my apartment last night after party. I hope _____ aren’t cold right now” it is clear that the sentence is referring to one person, but if I said “It’s chilly outside, I hope they aren’t cold.” you would have no way of knowing without having to ask who they are talking about.
IF in the post about appearance and diversity they were talking about say Hanzo, I would know that “they” refers to all characters, but when you add Venture who is a single person and also uses “they” in a topic that specifically talks about Venture it obviously becomes confusing unless you are being fastidious about it.
Maybe you can fault me for not reading through 600 replies, but you cannot fault me for assuming a different context because I could not find sufficient information in the sentence, after all, no harm is done anyways.
But that’s the thing… No one sane would say that two sentences together, because you don’t know who it is about. The same way no one sane would say “It’s chilly outside, I hope she isn’t cold.”
That sentence doesn’t work not because of they/them is singular or plural dilemma. It doesn’t work because there is no proper context to invoke pronouns instead of actual names in the first place!
You are looking for a problem where there isn’t one!
I always check past replies that the post is made to if I am not aware of context or something is confusing…
So yeah, I 100% can fault you for not doing the homework and then being confused why you failed.
This is really becoming petty tbh
Such a great rebuttal…
I think you convinced everyone 
/s
Because I feel like a broken record, you’re being obtuse, not my problem
Because there is no problem…
You creating a fake one just for the sake of it.
There’s no point going in circles forever, I guess we agree to disagree
(I still believe I’m in the right)
That people will unironically say “it’s cold outside. I hope she isn’t cold”?
No, you are not!
You know what I mean, don’t act dumb.
I’d reply again but it’s going to be 14th rewording of the stuff I said earlier.
Actually I don’t…
I really would like to know it you really think that anyone would say something like that…
here’s my reply:
(insert 15th rewording of the post I said 1 hour ago)
I’m too lazy to retype that shi again
Are you just trolling at this point, because you can’t refute the point that was made?
First you’re calling Trickster obtuse, now you’re saying you’re going in circles… Make up your mind!
What’s next, are you going to call Trickster a square?
God geometry jokes really are awful lol
Idk. For me, it’s a little funny boy, I can’t see girlish peculiarities, for me, it is just a junkrat but a sane one, that has fun doing weird things, but he is aware =)
I am a triangle, thank you very much!
I swear I’m not, it’s just my reply is again going to be exactly what I said earlier “English isn’t my first language, seeing they/them makes me assume they’re talking about multiple people, yada yada yada…” there’s no point typing it again, because you will say something you also said earlier, and I’ll have to reply defending my stance for the nth time, rinse and repeat.
Or do you really think this debate is going anywhere?
Then why you can’t address what actually was said?
why?
I’ll make it really easy for you.
Answer me this. Do you really think that anybody in their right mind would say “It’s chilly outside, I hope she isn’t cold” as an actual sentence without additional context?
I think it can. You just need to be honest. And not only with me, but primarily with yourself!
Looking at the context clues of the message itself and you will notice what it holds
If for example
had “Venture is too strong right now” before it, its fair to assume theyre talking about venture specifically
if it had “Ventures damage is too high” it is fair to assume its still about venture, since damage is an object in the sentence itself, it would be reffered to as “it”
“Ventures damage is too high, i hope they change it”
if however it was something alone the lines of “Ventures abilities are too powerful i hope they change them” you can assume either, either theyre talking about the abilities, or venture themself, because in this scenario specifically, it doesnt matter because the end product of the sentence means the same thing regardless of if theyre talking about the abilities or venture, as the target is ventures kit, and saying to change venture as a general thing means changing ventures kit.
In this again, using context clues helps you figure out whether theyre talking about heroes, venture, the dev team etc, if the topic of the post talks about venture specifically, its fair to assume its venture
If theyre talking about heroes in general, its fair to assume its the heroes
If theyre talking about the dev teams efforts to include diversity, its fair to assume its the dev team,
if they do not include any sort of implication on what they are referring to, thats on them for being unclear, it wouldnt matter in any other case to help the confusion even if they used she or he for say tracer, if they started a post with
“She can be diverse without being ugly”
We would have absolutely no idea who they are talking about until they refer to the object of the conversation itself.
If youre given a situation where you accidentally say a thing you didnt think was racist, some stereotype about a black hero, would you apologize to the hero, or would you say “oh my bad” to the person correcting you? or would you refuse to acknowledge that you were wrong?
Refer to my statement above
It is common courtesy and good manners to apologise when you make a mistake, be it in language, or actions, its basic manners at that, something nigh everyone whose civilized should have.
No, next to the fact that the poster themself can be wrong with the language they use, as many people dont speak english as their first language and dont how to refer to things.
And even next to that, a poster might assume that its clear who the apology in the scenario should go to since its common sense for most people.
Because a lot of the things you have said are incorrect, thus a mistake, one someone would naturally apologise for after making it and then correcting themselves 
In this specific scenario you would again take the context clues from the other parts of the sentence and piece together whether they were talking about a group of people or a singular person, and if they do not state that, then they are making the mistake of not disclosing who theyre talking about.
The same way, saying “Its chilly outside i hope she isnt cold” doesnt give you any way of knowing what theyre talking about, its something
Could be a friend of theirs named sarah
could be their dog Bailey
Could be their mom
could be the bartender from a bar they just went to
could be a cashier
could be- you get the point
Giving the object of talk at some point in the discussion is important when referring to people or things with just pronouns, as no matter if you use she he they it unless they specifically know what youre talking about, itll be a guessing game.
Ill reply to this! they wont.
Its an unclear implication of multiple things that make no difference or particular sense to an outsider of the interaction. Because for one
Its chilly outside while usually means directly outside where you are now
it could also mean if theyre talking about someone in another country, the outside there, since temperatures differ
The person in the conversation itself isnt clear either, again as i said before, can mean a dog, a cow, a cashier, a bartender, a sister, a mother, theres no implication of who its based on unless given the context clue beforehand or after, and in that case, if you know who its talking about, it doesnt matter if theyre reffered to as they, since you understand its about one person