This Is Big Brother Housemates Must Not Discuss Previous Series of Big Brother.
 

Why is this?

I find it intresting when they speak about past seasons like twists, tasks, housemates etc

Why is it not allowed?

I was thinking that too, they used to be able to didn't they??

They've never been able to; but why not? They would only have seen what BB permitted at the time anyway. - Therefore it's happened and been aired, why can you not discuss it?

Maybe it's a copywritten thing, they're 'mentioned' on a Television program therefore royalties need paying?

To focus on the current series and not any other series'.

Probably something to do with the All Stars

I think bb doesnt want to create an on TV comparison, like last time they did this better. Suppose an HM says last time they had twist which was much better, it looks bad on current series.

Again thats what i think

I reckon it's probably just to keep the conversation new and fresh. If all the HM's are talking about is previous series, then it's going to get pretty boring for us sooner or later.
It does seem like and odd rule at first though, I'll give you that.

You don't have to pay royalties when you talk about someone, even if it is on TV, I can assure you.

To keep the series "new", they dont like HMs talking about another series during a newer series.

Its a stupid rule :/