Attempted to share a post via Mastodon like this:

But I got an invalid link and a wrong text:

Clarification: The post I wanted to share is not about mental health and the link is broken.

Looks like your original post didn't contain tags.

But this post did, and I can see it when I browse:
https://mastodon.social/tags/piefed

I understand the issue is not about post federating into Mastodon, but sharing it (the arrow/paper plane icon at bottom right of the post)

Oh, okay. Looks like I need a Mast acct to do that. Someone have a Mastodon acct to test that?

I can replicate the issue on .zip too. With this post and another one. And even weirder, the copied title is something random

Okay, I made an acct and tried what you tried. I didn't get that error message, and here's the post that was created: https://mastodon.social/@JohnnyEnzyme/117360945059012498

The original link clearly got borked up, though.