"Chelsea Manning" is the preferred name that refers to the person Lamo reported. "Bradley Manning" is a former, non-preferred name. Nothing about history changes if a different name is used; the same person is referred to either way.
That you didn't recognize the person based on the preferred name only indicates that you've paid less attention to the news than you thought you had.
I'm rather surprised someone on hacker news could not have heard about Chelsea Manning in the past few years. (Or even just on the internet, really.)
If you have any interest in artificial intelligence and automation or their effects on society at large, I strongly recommend her Op-Ed in the Times last September [0].
Like her or not, she's a big figure in cybersecurity, freedom of information, and international politics. I thoroughly enjoy and benefit from what she has to say.
That you didn't recognize the person based on the preferred name only indicates that you've paid less attention to the news than you thought you had.