We 100% want to add an in-game report feature and it’s high on the list to be added. However, this wouldn’t work for gold sellers. They already get banned about as fast as they come in (I spend many an hour after work just watching chat logs banning gold sellers to try to reduce their effect). We need more automated solutions, and are working on it.
Having an automatic mute/ban after a certain number of reports is also extremely abusable. It has already been abused in other games where groups of friends will all report someone legitimate together just to silence them or get them banned because they don’t like them.