Why are there hidden strands in addition to this discussion?

I wrote a reply to someone who started a thread at the weekend. Later, I noticed the thread had vanished and I thought perhaps it had been deleted because it was not quality material. Today, I received a reply to what I wrote and the reply appeared preachy in tone. I sent back a response even though the thread appears hidden. Later, received another reply even though it looked as though it had been written to another person rather than me.

I am puzzled. I don't know why the thread is hidden. If it was a thread not to be continued why is still going but hidden ? Or, is this due to technology niches. I am not mentioning any names or the discussion to avoid any offence to the creator of the thread.