Sorry, can't make any sources, so long since I used model editing..
People do absolutly not get banned, for changing their characters race from orc to human, or changing druid forms.. These kind of changes, that have no impact on the gameplay, will be tolerated by blizzard, even if you stream.. because, no one really cases.. Altho, they did change how the game data is handled, so it is not as easy to model edit as it was in vanilla and tbc.
People absolutly do get banned, if they are found to increase the size of objects to make it easier to spot, or changing the world in ways to prevent other players from seing you or attacking you.. Things that alters the game in ways blizzard do not agree with, will get you banned, if you stream it to the world.
When you made your account, and every time major update takes place, you get to accept the ToS.. it is techincally against blizzard's rules, to modify the game like you do when model editing.. So, as have been said several times already, the chance is probably close to zero that you will get banned from doing simple model editing.. But there is a risk that it could get you banned, and you need to accept this, and stop telling people that people can't get banned for editing the game files..