With regards to the fact that it's part of another thread, I don't think that matters too much. If it were an update present as a separate document it would pass muster. There've been several open letters, and responses to such, and further responses again, etc that have been posted to HN. Furthermore there's no guarantee that someone reading the original thread will see this exchange; I read the thread after the exchange happened and missed it.

This is significant enough to be posted as its own item, that it's part of another, ongoing thread shouldn't take precedence over this significance.