Testing this method on posting to Kbin from Mastodon shows that the post will appear in the Microblog section when you:
@[community name]@kbin.social
Hashtag additions to magazines/communities on kbin are inconsistently publishing at the moment, so if you want to make sure your post gets published, use this method.
For those wishing to publish on the 13th Floor Microblog, include the following in your mastodon / pixelfed / tweet style post: