I don’t know why Mueller got to meet with Comey before his testimony without having someone from Justice to sit in on it or without a transcript. Trump should have ordered that. Even if you accept that they can have a special counsel on a non-existent crime, which I don’t, that doesn’t mean the President doesn’t get to tell them not to preserve evidence.
I can’t believe that Mueller or another investigator would tell a witness to prepare to do anything but answer the questions truthfully.
I am assuming that Mueller is a lawyer. I know Comey is a lawyer. One can claim that the meeting between Comey and Mueller was a legal consultation. That is what Hillary did with Cheryl Mills. Dems can’t have it both ways. Was it a legal consultation which makes it a definite conflict or was it an illegal meeting which itself created the major conflict/