It’s not an issue with how you did the link, I can view that thread on my instance but not the thread’s host instance see last bit.

Though there is an answer to your question: assuming it stays up, lemmyverse. (use fediverse icon link, remove https bit and plug it in)

For example, your comment on that thread works as a link: lemmyverse.link/feddit.org/comment/14366386

The fediverse link I get from that thread (https://piefed.blahaj.zone/c/asklemmy/…) is just wrong for whatever reason? (even wrong on host instance!)

This works: long link, breaks if you shorten it
This also works: piefed.blahaj.zone/post/911357 (found via get-embed-code option, this is the sort of link my own posts get)

So non-comment thread link: lemmyverse.link/piefed.blahaj.zone/post/911357