Comments moved thither. Thanks!
When two threads are covering substantially the same story, we often merge them to prevent split discussions and to prevent duplicate posts on the front page. Is it a fair practice? That's for you to decide. I think it is! Actually the community tends to get annoyed if we don't do it.
This is just standard/boring forum moderation. HN has done it for many years. Moreover we do it so often that if there were even a slight tilt of community opinion against it, we'd never hear the end of it. That's how I know the community likes it.