Michael Jackson Script (mjs) is a file name the node js community ascribed to ES6 modules.
An Update on ES6 Modules in Node.js on Medium is well written and well commented on page 
I am parsing through the article to understand more the complaints by the node community.
My gut check is, nobody has explained the capabilities-based logic behind ES6 modules. Thus the node community feels the standards people have not taken their needs into consideration. MJStwitter
When the opposite is true in Solidity: Race-To-Empty, Recursive Call, or Solar Storm vulnerability page
Some ECMAScript Explanations and Stories for Dave by Wirfs Allen blog
ECMAScript (ES) module loader that enables a smooth transition between Node and ES module formats with near built-in performance blog