[splix]

I like Asciidoc and think it's a perfect format for tech documentation. It has all you need for cross referencing in docs, great table support, notes, etc.

The main problem, as author has noticed, is the single implementation. That significantly limits its usage and support in other tools. And to my understanding it's because the owners of the format had overprotected it with trademarks and so on. So no one wants to make another implementation because it's easy to get into legal troubles.