They're allowed. The problem is, you flagged every red flag you could on the way in.
Your application to the instance was pretty generic. It said the right words but didn't feel as genuine as some others.
Then after joining, you didn't link to an existing account or community, you didn't engage with anyone else, and your first action was to create a community and a post linking to an offsite blog.
It's the same thing we see from blog spammers, which is what I assumed you were.
I'm happy to restore the post if you still want it, and if you plan on being involved with the wider lemmy community above and beyond making posts linking to an extremal site