Obviously, in the Harry Potter universe, some Muggles know all about wizards. The Dursleys, for example, and the British government, as well as Hermione's family. But at the same time, the Wizarding World has a vested interest in keeping themselves hidden, often going to extreme lengths to preserve the Muggles' ignorance about what's really going on. Some things (like this question) seem to take care of themselves, but word-of-mouth still seems like it would be an issue.
Are there any details provided about how they navigated this issue? Did Hermione ever mention (before the events of the final book where she straight-up mind-wiped them) an inability to tell her parents about anything she was doing? Was there a legal reason why the Dursleys could know about Hogwarts but Marge Dursley couldn't (aside from the Dursley's self-imposed shame)? Did we ever hear about family members' memories being altered after graduation, or any loose-lipped gossips needing to be told to hush up?