The reason I regard the Kenny/Duck bussing as a strategically bad play is as follows: Assume Agent did not find SK on n1 (what you'd probably assume) and that Kenny got lynched and "proved" Duck as not-mafia. The d3 scenario would look something like this:

Town
Town
Town
SK
Duck (mafia)

With one of the towns or Duck possibly cleared from being SK. In this scenario, if town is really convinced Duck is almost definitely not-mafia, then SK will almost definitely stab Duck on n3 because he'd think Duck is a safe non-mafia bet. If Kenny was lynched without the play, then Duck would likely not get stabbed and would be in a decent position to convince the remaining town he's the SK on day 4.

Obviously, if the play fails and Duck doesn't get much credibility, then Kenny died for nothing.