Is showing something public detraction? What about speaking of an experience of a heresy you heard uttered at the novus ordo? Would it be detraction even if you don't tell the name thus not damaging the reputation of the person?

Because of the crisis, detraction no longer exists. Epikeia. And supplied jurisdiction.

I am looking for a serious response

Detraction involves making something private known to people who have no business knowing it.  In the case of something said in public, such as in a sermon, or if the people hearing it have a vested interest in knowing it, there’s no detraction.  If you were revealing a private sin with regard to something that poses no threat of harm to others, that would be detraction.

So, for instance, if I caught a priest looking at child porn, I would be obliged to reveal it due to the threat he might pose to others.  Or if some priest is promoting heresy, I can reveal that too ... since he could pose a threat to souls.  Of course, I should try to correct him first and be very sure it’s heresy.

There are tons of factors that could weigh in.  Consult a Traditional priest with the details.

Is showing something public detraction? What about speaking of an experience of a heresy you heard uttered at the novus ordo? Would it be detraction even if you don't tell the name thus not damaging the reputation of the person?

My understanding is that detraction has to do with the role of being the revealer of, to a party without cause to know, a reputation-harming event that was previously a secret.  Covers what Ladis said, regarding right to know vs. no purpose to the sharing except to satisfy a non-involved party's possible morbid curiosity.
If a statement has been made public, the person who uttered it is himself the revealer. 

Now, that said, we have to examine our consciences as to our motive for bringing the announcement to the attention of another or others who didn't hear it.  If it's to protect the recipient of the secret -- someone who could be misled into thinking that a particular priest is orthodox when he is not, and we are sincerely worried about scandal  -- I see nothing wrong with voicing your concern.  OTOH, if our motivation is simply to criticize and discredit the priest, to injure him out of spite, anger, or hatred -- then I would regard it as a sin, but not the sin of detraction -- since the priest, not you, was the original revealer.