In this case, the negative didn't outweigh the positives that the town received.
Option 1: The day ended with the execution of an innocent player. Then, the second player, who was suspected, was the Mafia. Result: -1 innocent, +information.
Option 2: The day ended with a modkill of an innocent player; he said that the other player was the Mafia. Result: -1 innocent, +information.
In my opinion, it's equivalent. Except for the action itself, of course.
Цикл "Закадычные враги": "Особенное гостеприимство, "Супероружие", "Меж молотом и наковальней"
"Падение Шантири"
Кампания для "Кодекса Войны"
"Выбор Сагиттеля"