Help me out with a super-injunction please

Maybe I'm being a bit thick!  But I really don't understand how a super-injunction can possible work in the day of mass-user digital publishing.

Here's my query.  Let's say I've seen person X doing something very naughty, but not illegal, on a number of occasions.  I decide that I'm going to blog about X's behaviour because that person has been very critical of other people doing the same thing and I believe that X is being hypocritical.  I go home and blog about X being very naughty, unknowing that X has a super-injunction preventing people discussing his/her naughty behaviour.

If what I had written was a lie and damaging to X, I would be looking at the wrong end of a libel suite, and rightly so.  But if X wasn't being naughty they wouldn't need a super-injunction.  If what I've written is true, and I can prove it to be true, I can use the first and most powerful defence against a libel action which is to prove justification.

If I have never been served with the super-injunction covering X's behaviour how can I know that there is a ban on their actions being written about?  Surely I can't be held in contempt if I was unaware that the injunction even exists.  If the court issues the super-injunction to everyone who could potentially publish the story it would need to go to everyone with a blog, twitter account, facebook page etc. etc. etc. rather defeating the object of the super-injunction.

Maybe I'm missing something really obvious and if I am please let me know.