Unfortunately, that journalist is being investigated for crimes so that is somewhat inevitable. This also, is the opposite of a journalist going to jail to protect a source, Manning is the source and everyone already knows that.
Which, it's worth pointing out, Manning has also said that she's willing to testify, but only by light of day, not behind closed doors.
That's supposed to be secret in grand jury proceedings; the only thing that is supposed to become clear is what (if any) charges they are indicted for as a result.
> it's reasonable to wonder why the prosecutors have worked so hard at avoiding any exposure to the best disinfectant.
Because they are required (both by the law around grand jury process and long-standing administrative policy to protect all of the reputations of people who aren't charged, the fairness of process for those who are charged, and the integrity of law enforcement and any other related investigations that might overlap with the present one but be in different statuses) to not make public most information pertaining to an investigation where an indictment has not been returned yet, and also specifically to preserve the secrecy of the proceedings before the grand jury.
> Which, it's worth pointing out, Manning has also said that she's willing to testify, but only by light of day, not behind closed doors.
Which is simple PR; federal grand juries considering criminal indictments cannot operate other than secretly.
Incidentally, this exact policy was why tables were flipped over The Comey Letter/press conference. When the FBI decides not to go forward with charges, they aren't supposed to say jack shit.
That's not why it's secret: it's not a case-by-case, sensitivity-based decision. Criminal grand jury proceedings are secret, period. This protects suspects, it protects witnesses, it protects the integrity of law enforcement investigations, it protects third parties who might be mentioned in evidence and testimony. This is a long-standing rule that applies to all criminal grand jury proceedings.