>> heluecht:

“When calling https://hotpump.net/api/user/heluecht/inbox before, there was no comment from you at all. I would have to poll the "proxyURL" from time to time, since there is no notification at all.”

No, you're not supposed to get activities done by people you don't follow (this is a point that needs enhancement, and it's actually addressed, I think, in Owen's 'demo' spec).

But if you query a public post's replies, you'll see every reply, no matter who you follow.