He should code in HTML properly.
Code alignment and indentation isn't done to make the code look pretty, its purpose is to organize everything, so you can find what you're looking for faster. It makes no sense to take advantage of it AFTER you've finished lol
Those tools should be used just to check if you messed up, don't make him create bad habits - specially when the websites you code have +100 validation errors.
The url Kw3rLn shared with you is really useful and you should read it, in my opinion.