Re: some implementation details
I don't disagree a bit with you that many people you do not know will make superficial judgements about you, much of that based on how you look. I would not wear a hoodie and sweatpants even to a job interview at Facebook, even though the founder dresses that way. If it is important to you what people you do not know think about you, by all means they should follow your advice.
My points are directed towards already having a job. And I'll leave Fortune 500 out of this, those companies are so big you know people just about as well as the people you see in a New York subway station. You are constantly making a first impression in a place like that, along with dealing with constant politics and CYA behavior. You better "play the game" if you want to work in place like that, and your advice is something you have to do if you goal is to rise thru the ranks. Heck, since many of them throw out the 10% they don't like every year, you better do it to survive.
But for the rest of us who work at SMB, who our coworkers become like family, this dress up idea is senseless. It has nothing to do with being "professional". I design systems and write code for a living, I guarantee you I'm as professional at that as anyone you will ever meet. But you can't convince me how I dress has anything to do with that. If my applications work and make my coworkers jobs easier and more efficient, make our company easier for our external customers to do business with, no one cares that I get that done in jeans and t-shirt. This is a forum for IT people, not salesmen and HR.