Don't be Fediverse HOA about people promoting their own work on here. Don't make people who are just trying to make a bit of money from their art, or get the word out about a talk they gave or a project they just released, etc feel unwelcome. Do the opposite, even.
If a person is actually an unscrupulous grifter then trust that they are due other social consequences that have little to do with something plenty of other people manage in a reasonable sociable way.