@jerzone
1/N
As I understand it, here's how hashtags work.
You can see any message with the hashtag that gets to your server.
How does it get to your server? Someone on your server has to be following the author. If no one on your server is following a post's author, it's not going to get transferred to your server, even if you follow that hashtag.
Group users on the other hand, propagate better- details in followup post