I had this experience watching Eddington. My adult son and I were laughing all the way through and the packed audience was totally silent. Very strange experience.
I'm happy to report that the 100-200 humans filling the room were laughing throughout the film, and all at appropriate times. The plot really began to peel an absurd onion, and things got quite meta, and we just kept laughing along with one another. It was a very good time, had by all.
As for the film itself, I thought it was quite engrossing, and I am glad that I hadn't seen any real spoilers, because the third act was definitely a doozy. And it didn't feel too long, or dragging or tedious. I thought that the entire question of what's real, what's deception, what is believed, especially by Holmes and Fielder, were very well-explored in this.