Maybe a tag in the original title could also help? Something like: "[FAKENEWS] When a customer refunds your paid app, Apple doesn’t refund the 30% cut"
People not reading the comments will then have a way of knowing this is false information.
Terrible tag idea, it's implicitly negative and accusatory. In this instance, the guy was apparently just honestly misinformed.
The main problem is that most of the original thread ballooned with upvotes because it became general "<big corporate entity> is bad" kvetching which is perennially popular and probably doesn't belong on HN at all. As long as these kinds of threads aren't modkilled, these things will happen, you just have to deal with it. Tagging them won't solve anything.
Technically, it is not known what the consequences of an untried action might be. There are many possibilities, that vary according to differing circumstances.
The article is not fakenews. It covers a research about anti-climate statements. Those can be fakenews (though depends on the nature of the statement I would say).
When you wrote this comment had you read the journal article to see if the Press Release and Press Release Title linked on HN accurately represents the published journal article?
People not reading the comments will then have a way of knowing this is false information.