"Is it surprising that the chief of the criminal division in the U.S. Attorney's office wouldn't know her comments would eventually be traced back to her?"

"With all the emphasis DOJ puts on its cybercrimes task force, and its use of subpoenas and court orders to get social media and email account information about those under investigation, why would federal prosecutors feel secure enough to post under a pseudonym?"

The arrogance... the stupidity... If you're going to be arrogant+stupid, watch out for the idiosyncratic punctuation:

[T]here were multiple instances in which the online comments and Mann's pleadings contained an extra space after a closing quotation mark and before the final punctuation period. Other similarities included the lack of spaces before and after the dots used to designate an ellipse.