I thought I'd find this easily on my own but it seems I'm the only one who finds banging on the wall constantly annoying? Does a mod exist to just stop this altogether? I do have a mod that prevents noise waking up sims, but this doesn't include the noise through walls by neighbours.

Nope, you're not the only one. There are a couple older wcifs asking for this. Unfortunately, a mod doesn't seem to exist to stop it completely. someone did mention that you could absorb the noise by putting lots of furniture against connecting walls between apartments. If you're building your own apartments, maybe putting a 1 tile wide space between apartments would work.

Yeah, normally, the noise emitter can only be on a "bangable" piece of wall, although I only rent apartments where it's possible to have bedrooms that don't share a wall with the neighbours. I don't like having an entire wall hidden by deco and furniture.

What a stupid feature, AL developers must have been raised in castles, if they think that it's impossible to sleep in a room that shares a wall with another flat.

It's not what you asked for, but noise can only travel through empty tiles. If you place invisible paintings on the wall, it can't transmit noise. Won't stop the noise your sims send to neighbours, but it will stop their noise coming through to your Sims apartment.

or maybe they assume apartment walls are made out of cardboard or something

You can go into moveObjects on and delete the noise things

I remember one time the neighbors were blasting a radio or tv almost constantly. I left the apartment I was at, entered the one next door and they didn't have a radio or tv. Another of EA's 'not thinking clearly' ideas.

Invisible paintings will do. What annoys me more is that not every neighbour is a loud selfish moron (currently dealing with nightmare neighbours in real life so had to get that out). I make a lot of my sims the shy and/or quiet type so this isn't realistic IMO. They could have at least made it so only highly outgoing sims are noisy.

Or mean ones.

I build my own apartments - that stupidity being one reason. I hate even more the complaining neighbors waking the family up OVER AND OVER; not sure what caused it, smelly babies, dishes? Was that what you said their was a mod for? What's it called?