Redaction: While it is possible that Mormon created dialogue, it seems that he prefers to copy it from his sources. Of course, the author of the source document may have exercised creativity (or literary formulae) in recording the dialogue.
In this particular case, it seems to be authentic to the period. Rather than tersely introducing the topic, Gideon gives an elaborate introduction why he should be allowed to speak. He reminds the king that his valuable past services and useful advice. Of course, Limhi already knows this, so Gideon’s introduction is entirely useless as information. However, it is entirely appropriate as revealing the protocol required for a formal occasion. Mormon’s style tends to be more direct. If Mormon had invented this speech, he would have more likely moved quickly to the point.