[Nyx]

How will it drive members away when they are completely different niches, not competing not anything close to similar as Sinisterly.

If members want to leave they will leave no matter what all it takes is a google search to find another similar forum.

Even if it is a completely different niche as you say, members will begin to spend more time there posting and being active if they enjoy it more, thus driving away members/making them less active. I completely agree with the rule, I think it should stay and should pretty much be a base rule on any forum.