Yeah... How do I get to choose what I share? How would it work for HN or Twitter? Do they have to support this? Where should they start to be able to support th

Yeah... How do I get to choose what I share? How would it work for HN or Twitter? Do they have to support this? Where should they start to be able to support this? Again, how am I going to choose what I share? Who exactly has to implement it? I really need some details. If we actually have to rely on Twitter implementing something like this, then I do not have high hopes, as they most likely would not want to implement something like this. :)