"Deadnaming" is explicitly using the birth/non-current name of a trans person. The article does that, and also uses "he" throughout. Both of those things are typically seen as quite offensive by trans people.

I don't think a site-wide ban of the person who posted the link is reasonable, but it is a shitty article.

Mainstream UK press has serious problem with TERFs, so my question was genuine: is my understanding correct, that the issue stems from someone linking to misgendering, dead naming article?

I seriously doubt that. This is a claim I've seen in many places (unsubstantiated) but I find it hard to believe that her name is triggering bans. Dead name? Sure, I can believe that and, again, I have no problem with this.

That's some Chinese Communist Party level censoring.

You could but you, obviously, don't have to. The problem is not about the content though, it's about linking to it. So someone linking to this old article if there are recent, better sources could very well be doing it maliciously.

Think of it this way: if someone linked to an old article that used some slurs that used to be mainstream-acceptable at some point but aren't any more, would you feel uncomfortable? I hope you would. The reason people don't have this visceral reaction when it comes to trans people has a lot to do with broader lack of understanding of non-cis minorities.

There's an obvious problem with figuring out what the intentions of someone writing are. And we absolutely can't tell if e.g. someone dead naming is doing it on purpose or not. Not knowing and willing to learn is absolutely fine. But since you can't tell oblivious from malicious, you have two options: ignore assuming innocence or ban assuming malice.

Internet discourse is not courtroom, you don't have to assume innocence and it's absolutely fine to have a higher standard for communication on Reddit. Not that I think Reddit does, but it could. ;) So, again, what should you do with misgendering or dead naming? Since I sympathize with minorities and the oppressed, I would ban. But I'm absolutely sure many, many people would find a way to label what I'd considered hate speech "a freedom of speech issue" so I'm not at all surprised that this is causing a stir over on Reddit.