There is one thing that is completely unacceptable in the ISM--misrepresentation. People generally realize that many clergy are no different from other people. We all have our foibles, our short comings, and wrestle with different issues. However, misrepresenting ourselves cannot be tolerated.
In mainstream denominations, clergy misrepresentation is (sadly) more common than one would think. Besides the scandals, there are the cases of the made up diplomas, the credentials that don't really exist, the ego inflation... But things are a bit different in the ISM. In the ISM, the principal sin of misrepresenting ones self is the misrepresentation that one is a Roman Catholic, Anglican, Orthodox, etc. priest.
It should be noted that this rant is not pointed towards traditionalists who have split (in the eyes of the establishment) or continued (in their eyes) from their original tradition. They are often very clear that they are not connected with the "official" church. This may also be evident because of their calendar, commemorations, position on the Pope, liturgy, etc.
It is directed towards those members of the ISM that are so delusional or seeking validation that they present themselves as a priest from one of the above groups. Often, it is most prevalent with Roman Catholicism. I would posit that is because much of the general public is unaware of Orthodoxy and so it is more difficult appear to misrepresent as a "canonical" Orthodox priest. This is especially true in light of the many various factions and the traditionalist issues above. The same, too, with Episcopalians as many simply call themselves Anglicans and people (generally) know the difference. Most Roman Catholics, frankly, lump Episcopalians into the Protestant category and most clergy from the Anglican tradition have no problem telling of the differences between ECUSA and them.
I have heard horror stories of ISM clergy misrepresenting themselves as Roman Catholics. This includes independently ordained priests hearing confessions in Roman Catholic churches until ejected, showing up at liturgies and presenting themselves as Roman Catholic clergy, saying mass and running off with the collection plate, etc. Sometimes, these folks are pure con artists. Sometimes they are mentally ill. In every circumstance, though, they should not have been ordained (if they were). The same goes for those who misrepresent themselves to faithful as Roman Catholic parishes when they are, in fact, independent parishes.
I have also heard every defense for posing as clergy of a larger jurisdiction. "No one will come to our Mass if we let it be known we are independents" or "They don't know the difference" or "I'm valid, so it's ok." To be clear: it is never acceptable. Those priests are misrepresenting themselves and lying to the People of God. They do themselves a disservice and they create suspicion within the community about our movement.
Sure, there are occasionally those folks who don't know about our tradition and may be confused. This is a teaching moment and when I have met such folks they often come back to the liturgy. This is because our understanding of our faith and the liturgy resonates with them. It is often difficult to describe ourselves in a short period of time. People get confused easily about our tradition. What is not ok is to misrepresent.
The larger issue, as well, is why one would want to represent themselves as a Roman Catholic or any other tradition mentioned. We have an extraordinary calling--to minister to those who feel lost, abandoned, and need the Sacraments and liturgy that feeds their soul. We can function outside of dogma and man-made rules to help others become connected with God. That is a greater gift than a momentary bit of recognition or a photo opportunity.
"But if you have bitter jealousy and selfish ambition in your heart, do not be arrogant and so lie against the truth." James 3:14