The votes are in, it is bad UI! Thanks to those who commented and made suggestions.
I have no idea why, but somehow my site became the target of bots signing up, with legit looking emails but username was random letters. I already check for emails, so a friend suggested putting a hidden trip field for the bots (this is apparently common?) and I thought it might be fun if I made it visible.
The field totally worked though, the bots gave up. Still annoyed though, who was it? I didn’t post the links to the site in many places yet it’s work in progress, I have like 10 (human) users. I guess I need to add some IP blocking and all sorts of other stuff too in future (eg captcha).
And yes the DDG thing was put there by my browser. It’s a handy feature, gave me multiple free trials on ChatGPT for eg, before they stopped the new sign-ups!
AI models get more dishonest if you ask them to respond as if they were a pirate: https://www.circusscientist.com/2023/11/13/i-hired-a-pirate-to-take-orders-for-my-entertainment-business/