The post seems fake, and even if it wasn't, this is kinda the point of Bitcoin.
Just remain anonymous using pseudonyms and perform transactions in Bitcoin.
I doubt they are going to be able to dox you well enough if you use a different pseudonym for the microsoft keys related transactions, and even then I'm not sure they'll be able to know with certainty that they're suing the right person.
I have took a quick look at this post, it seems he did sold on Ebay and sold not only the key but as well the DVD's/CD's pretty dumb to do so, but a few users said that this letter is not fake.