I can't say I've noticed disruptive teenagers in lounges. They usually tend to be glued to their phones getting in some last minute Snapchat, Yikyak or whatever before heading off.

As for babies, I have never seen someone change a poopy diaper in a lounge but as a parent of one and soon two children with poopy diapers, I'd say that's going a bit too far. Most airports have a healthy supply of family-friendly washrooms with sinks, so I wouldn't subject fellow passengers to a display of my kid's waste. That's not just a lounge thing, I wouldn't do that anywhere else in the terminal outside of a washroom or baby changing room.

But that said, I wouldn't take great offense at it either... I mean, I can handle the sight of a poopy baby... I certainly wouldn't start a scene over it.