Be very careful about personal allegations and attacks.
PPRuNe is totally behind exposing companies and courses where people have been ripped off, but with that comes a responsibility to have hard facts and attributable comments, which might be depended upon in court.
If you can't commit to having your real name and contact details available (not posted on the site publicly, obviously) should legal action arise against PPRuNe, then your comments may not be allowed to stand.
Truth is, of course, not libel, but you may have to prove the truth to interested authorities.