I can’t comment on parent posts as the option just doesn’t show up. Am I missing something?

There’s a text field in the bottom with your username in grey that you use

Do you have a text-field at the bottom of the screen saying “whinestone_cowboy: “?

It’s very non-obvious, I think, but it’s there — completely different interface to the ‘reply’ button on comments?

Apologies if I misunderstood what you’re asking but the main post doesn’t have a reply button, instead the option is just available by default. I’m seeing all other replies with the option to reply so is this what you mean?

Test