Inter thumped Milan at San Siro 5-1 on Saturday.
Stramaccioni later said: "Going under the Curva you can do it or not, congratulations to those who went. Making a move like Leao did after the 3-1 is something I underline due to the esteem I have for the player.
"The thing that is annoying, as a coach, is that it seems that Leao is angry with part of the team: the gesture of (Mike) Maignan, who takes off his gloves in annoyance and leaves, fits in. He's angry, it's part of football: there it is.
"Leao's gesture is made by a player who can become an absolute top at European level. But this comes from mental growth: the celebration after the 2-1 is not anger. Leao was already unhappy with what was happening and the celebration is almost one of satisfaction: he doesn't go to get the ball. Yet it is the goal that makes it 2-1, it is the one that can reopen the derby, and after this opportunity Milan has another one, when (Simone) Inzaghi then roars and changes the match with the substitutions that close the match."