I can see how, if all you ever were exposed to was that link and this post, you might think they are equivalent, and the conclusion is "whatever, everyone is stealing from each other.
But the answer is no, Claude didn't train itself on ChatGPT, but Kimi K3 did train itself on Claude.
There has been no accusation that I am aware of by OpenAI against Anthropic, (which are in the same jurisdiction, so it would amount to legal action). On the other hand there have been accusations with extensive detail by Anthropic on how chinese models are attacking Anthropic to reverse engineer and copy their product.
There's nuance if you care to see it, but maybe it's easier to pretend that everyone is ripping each other off so that you can consume a ripoff without seeing yourself as at fault.
when open source models are banned maybe i will become a cartel kingpin smuggling open source weights into the usa. find a sufficiently shifty street corner, 'what do you need', "kimi". are you familiar with my product? pure mxfp4, $500 per TB.
(joke and walter mitty, i know the government reads my messages)