I think I finally got ActivityPub support for this blog working. On Mastodon, you can search for @en@jlelse.blog and @de@jlelse.blog to follow the English and German blog. You should also be able to search for the URL of any post and reply to it. But remember that it’s only possible for the reply to appear in the “Interactions” if your profile isn’t locked (so your reply is visible to the public). I will write about my implementation later, when I’m sure everything is working correctly.