@freemo @clacke

As i understand it from the post, it's actually a nice feature - the optional blocks.
It doesn't mean that a software will have some blocks by default, but admin will have an ability to block some instance "optionally". For example, you blocking poa.st cause your users tired to see these siegheiling fuckers in their mentions, but since the block is "optional", any user can unblock it for them personally.
It's like a "personal block" of the domain but only the other way around, a "personal unblock"