Not to mention that the letter throws a lot of hits but the hits may be weak, imo, because there are no lists of recorded incidents. Well, at least that we see.
If you want to have recourse for wrongs, especially if the person about whom you are complaining is a superior, then it’s a good idea to write down in the finest and most scrupulous detail exactly what happens or what is said. If it is recorded, like in a letter or email, then enclose a facsimile copy (letter: photocopy, email: screenshot and possibly forward it electronically). If you have an audio recording, forward a copy. If it’s an incident, again, be scrupulous about recording every possible detail: time, date, what happened with as little editorializing as possible, location, who was present, maybe who wasn’t present, etc.
If you just say, “I feel bad 'cause X is a meanie,” well, it’s very easy to blow that off with, “Be a man.” But if you document a continuous series, a pattern, of behavior, then I think your case is much stronger because it can show a defect of character.
While I say there should be little editorializing, you can still write about negative impacts on you and others. Just don’t exaggerate.
Sometimes there are emergency situations like sexual abuse and other serious acts that should be talked about right away, who cares about recording it, because the police will do that. However, crimes are a minority situation.
Disclaimer: I don’t have any personal interest in this and I have no idea whether the allegations against the Bishop are true; my statements above are just general common-sense guidelines imho.
What I really don’t want to see develop is an environment in which bishops have to tread very lightly for fear of being bashed and thrown out of their dioceses for increasingly pettier and pettier things. Bishops are fathers, not store managers.