so any offensive character who discards top card is cbn?
No. Discarding the top card can be negated, unless something else says otherwise.
Jephthah is cbn?
No. Jephthah's ability can be negated. If it is, the top card is returned to your deck, and the two EC's are returned to territory.
Any enhancment played through Hidden Treasures is cbn?
Not unless the enhancement says it is CBN.
and jacob playing enhancements pre block is cbn?
Not unless the enhancement says it is CBN.
I think you are confusing some correct rules which are similar with these assumptions. As YMT stated, the only abilities that are CBN are the ones he listed. However, there have been some rules made which make some of those situations close to CBN. For example, the enhancement that Jacob or a green prophet plays pre-block can be negated in general, but the ability to play that enhancement (i.e. Jacob's ability or Hidden Treasures' ability) cannot be interrupted (effectively CBN once it is played and hasn't been prevented). And if you choose the blocker pre-block (i.e. you use Obedience of Noah on Jacob) then that ability also cannot be interrupted. This was ruled so that you wouldn't have confusing situations where cards are unplayed.
Does that help?
