Only been a Ham for 2 years, but the etiquette I've observed falls along the lines of "don't do things that make it hard for other people to have fun". Like checking to see if the frequency is in use before sending, and not blasting out a wide signal when a narrow one will do. Respecting band plans, both formal and informal, especially digital people sticking around established watering holes and not splattering the CW areas. Don't tune up (sending a tone to configure your antenna tuner) on someone's frequency.

Another part is "let people do their thing". Like if someone's in a special activity and managing a pileup (lots of people trying to call), just give them the exchange and move on.

Due to the asymmetric nature of propagation, stuff happens. You may not hear anyone using the frequency but they hear you just fine. If band conditions take a turn for the worse, politely tell the other person you're losing them and thanks for the conversation.

Anonymity is banned; FCC part 97 says you have to use your call sign every 10 minutes and at the end of the transmission.

Ultimately the FCC is responsible for enforcing these but of course don't have the time. People can report people to the FCC and they _may_ open an investigation depending on that nature of it. There's also the ARRL volunteer monitoring program where participants listen on the air and, through the program, send out notices of good and bad behavior, optionally referring cases to the FCC. It's usually stuff like "guy constantly being a jackass on a repeater and ruining it for others", with a good bit of "sending outside your privileges" and "not identifying yourself".

That said we've all accidentally sent outside our privileges, we've all stepped on people. It happens.

As amateurs we know that if we don't do a good job of operating we'll lose the spectrum, so it's usually not a huge problem. There are jerks, there are also people that don't know they're being jerks.