Greg Jarrett (FOX News Legal Analyst) said last Friday that Comey's self-righteous Tweets put him in incredible legal jeopardy should he be investigated/indicted.
My guess he is being "ordered" by his handlers/pay masters to do what he is doing. They bought and paid for him, they expect pay back.
There was speculation on another thread that he's signaling things to people. He never expected to be on the outside.