I Received A Trademark Complaint

As the title says, I just received an email from Steam saying that someone submitted a trademark complaint against me, so I'm seeking a bit of guidance.

The person claims to have "common law trademark rights" over the name "Nieve Studios" because he has an itch io page with that username, where he posted a few game jam submissions. Now, as far as I know, trademarks can only be granted after you sell a game, you cannot trademark a username or anything like that, so he wouldn't really hold any rights as he didn't use said name for commercial purposes.

I published my game demo 6 months ago, and the final commercial release almost 2 months ago, using "Nieve Studios" as the publisher name since there was no account with that name on Steam.

Can this person really get me to change the name of my developer profile and publisher name considering they never released any commercial projects with said name?

It just feels kinda dumb how they raised this complaint when they haven't posted on any social media since 2021...