GNHQ guidelines state
"We don't generally delete whole discussion threads, unless they're libellous or racist or otherwise break the law, because it's frustrating for people to write carefully considered responses that, minutes later, are removed."
As far as I can see there is no mention of deleting "threads about threads"
Just what do GNHQ consider worthy of deletion? Insulting another member's intelligence or insinuating a member is a liar all appear to be allowed.
The criteria of what GNHQ finds acceptable seems to change depending on who is admin. for the day
Being quizzed by chemist's assistant in Boots.