Sampappalāpā does not mean “small talk.”
– You can see from some suttas that the Buddha himself first engaged one in “small talk” before that person would ask a question. That is being polite.
Palāpā mean “untrtuh” or “adhamma.”
– When used in conjunction with “san” that also has implications of “lobha, dosa, moha.”
– Sampappalāpā probably derived from “san” and “palāpa.”
Sampappalāpā most often involves rattling off on funny, vulgar topics or where one is disputing the truth, i.e., dhamma.
– Even in some serious discussions, when one takes a position against rebirth or non-existence of gandhabba, for example, that could count as sampappalāpā because that is making dhamma to be adhamma.
– Not realizing the truth is not an excuse. This is why miccha ditthi is the worst type of akusala that can make one reborn in an apaya. That is because one’s actions, speech, and thoughts are based on wrong views.