Understanding spark registration flow

I'm trying to figure out the flow and logic (and files used) behind Spark's user registration process. I have gone so far as intentionally commenting out blocks of code to try to force the registration process to break and it still registers users. In short, I am trying to NOT automatically register and login new users until I verify their email address. I've commented out just about everything in the various controllers/auth/registerusers files only to realize that I really don't understand how the spark-induced registration process actually works.

Yes, I try to intentionally break things so that I can really understand how they are assembled!

Am I supposed to be messing around with anything in the app/spark directory or even worse in the vendor/laravel/spark/src directory?