The part that actually matters in a Reddit link is the post ID, which is llgzv1 - the subreddit doesn't actually matter. You can put in just reddit.com/comments/[id] and it will take you directly to the post. So I think that ChatGPT has just hallucinated a URL with a random post ID.

Yeah, but it's happened 4 times or so in the last month. Generally they are dead, but the other times they are this.

See the link at the bottom the subpath is

r/MachineLearning/comments/llgzv1/diy_4x_rtx_3090_deep_learning_rig/

At the moment it leads to a NSFW OnlyFans thing:

https://streamable.com/z7lx72

And this is not the first time I am seeing this.

EDIT: diy_4x_rtx_3090_deep_learning_rig is just the slug. So it does not matter. Though it is interesting its happened a few times now. Does any one also see this NSFW redirect?