Sacred Haven of Debauchery

Areg, that's amusing! What you described… it’s not surprising at all, and frankly, it looks rather average. For example, at the Stade de France, Mylène's final song lasted 11 minutes because she sang with the audience for 5 minutes, then there were 4 minutes of just the stadium of 80,000 people singing, and finally, a 2-minute epilogue: decaying corpses, representing the transience of existence, descend, bowing before Mylène. And I won't even mention the Stade de Genève! There, the power to part of the equipment was automatically cut off due to the vibrations: everything shut down. There was no music, the microphone didn't work, but the stadium was singing… And as for "Rever" (although, any song from the "Ballades" album could fit here)… Mylène sings, but can't hold back her tears: she stops, and since the audience sings the entire song, they pick up the unfinished part, which Mylène then sings again.
P.S. And I won't even mention the arrangements that are different from the original! Many performers use this practice.