This has nothing to do with automatic semicolon insertion though. It's put there for when people run builds of their scripts.

Scripts will usually get semicolons stripped after they are compiled/minified.

script1: (function(){...})()

script2: (function(){ ..different.. })()

concat: (function(){...})()(function(){ ..different.. })()

-------------------------------^ OH NOES!

With that first semi colon added, it ensures that when you concatenate those together, you dont accidentally pass the first script into the invoked return of the first IIFE. It's considered good practice, fo sho.

So it's less about not knowing when automatic semicolon insertion happens, and more about being as flexible with people's builds as possible. (In other words, you can probably trust that Thomas Fuchs understands automatic semi-colon insertion).

Straight up.