In reply to Miroslav Glavic.

What’s to stop HeroPress from ignoring anyone who criticises them?

Nothing. But this has nothing to do with whether there's an app to block comments.

Threatened to “black list” me. ... This is sort of censorship.
...
I understand spamming/trolling but outside that it is censorship.

No, it isn't. There is nothing to stop you from publishing your comments, complaints, diatribes, rants and tirades elsewhere. No jack-booted thugs are going to drag you off to the gulag. You're not going to be served with a subpoena to appear in court. You're not even going to get a visit from the local bobby (British slang for policeman) to give you a mild ticking-off (British slang for a scolding).

On my site which I pay for and spend my time setting up and running, I can delete any comments I want, and block or ban who I want. That is not censorship.