He's published a book and wanted to let the world know, without even a 'buy here' link. If I'd publish a book I would be so proud as to even shout it out in the street to strangers!
That's, by our policies, totally fine as long as it is not his only interaction. I'll skim through his post history later to make sure this isn't the case.
He has little followers and following, if he's just trying to advertise stuff he's doing an horrible job at it.
While we give high value to respecting a disengage request, as I see it he's free to follow, and mute, who he pleases. If you don't ever want to see him again or have him to stop following you just block him.
QOTO: Question Others to Teach Ourselves. A STEM-oriented instance.
No hate, No censorship. Be kind, be respectful
We federate with all servers: we don't block any servers.