I do my first steps with activity pub. It looks like a really interesting piece of software.

Now i can follow some user and so on. Works fine.

Next i will, when i post on the Fediverse that this post landed in an category (NodeBB).

In documentation i find this.

Whether a remote user can create a topic in that category by mentioning it

So i send this post.

#ActivityPub Testing

@Radfahren

Now i think that this post will be move to the category Radfahren

The post will only be landed in /world.

What i do wrong?