The issue with that thread wasn't the topic, but the way in which the poster went about it and the way they responded. Without getting into too much detail (I don't want it to seem like I'm tearing into the person, just discussing what turned me off of that post), the OP of that post went into great detail about what asexuality is and why they think Nidalee being asexual might make sense (which is fine, although it felt like they made a lot of assumptions), and the thing that really irked me is they assumed most people (cishet as they called them) wouldn't like or care about something like this and would disagree on the basis that they were "cishet". There's nothing wrong with being "cishet" just like there's nothing wrong with being asexual or "transhom" or anything in between. No one can choose this, and these people are as different from each other as anyone could be. Obviously some people care about this stuff, and maybe they don't agree based on other evidence.
The point is, these subjects easily become touchy, because as soon as someone doesn't agree, it puts them in a bad light even if they don't agree for reasons unrelated to their feelings on asexual/LGBT+/etc. For example, someone in that thread stated "since Nidalee was raised in the wild by cougars, wouldn't it make more sense for her theme and character to be sexual of some kind? Especially since in old lore she was one of the few that was established to have been in a relationship?" and this poster was basically told their opinion was wrong. Not disagreed, WRONG as if they don't want asexual Champions altogether.
The OP's evidence for asexuality was that "she didn't reciprocate Neeko's feelings" and as soon as I say "what if Nidalee just didn't have the same feelings for Neeko as Neeko did for her?" then I'm somehow against asexuality. And I don't like that. You will also occasionally see people who DO push back against the whole "representation" notion and are almost always rude about it. That is the problem with most posts of this nature. Tension become high very easily.