A non-Christian is travelling with a priest and seeks his moral advice because he is available. Since the non-Christian was never Catholic, do the rules of confessional seal apply anyway when he reveals is dilemma before the priest?
"Seeking moral advice" is not a confession, and so would not be subject to the strict seal of the confessional. However, if there is no need for the priest to divulge anything, then I would certainly expect something said in confidence to be kept confidential.
To give a concrete example:
If moral advice was sought as part of a sacramental confession, then everything said is under the seal. For example, a question "When does exchanging information change into being gossip?" might be useful if you have confessed to gossiping. The priest may not need that question, and could well give the advice anyway, but there's no harm in asking for guidance.
You could simply ask such a question outside the confessional, and receive the same advice. And I would expect that to remain confidential: if there is no need to recount your conversation, to do so would be gossiping.
See also Are non-Catholics allowed to go to confession? — although that presupposes that the penitent is at least a Christian.