This bit is crucial: "Missing credits - One of the confusing things that I found tedious was the lack of credit in pieces and projects as to who did what. It is not only hard to evaluate your contribution but also what you are capable of doing. It is also very unlikely that you did the whole project by yourself and if so, say so."
This is really prescriptive.
As an aside, i would be dubious about following advice from a blog that also describes the latest Pepsi logo as successful.
Missing credits - If there are no credits, I'm going to assume everything was done under someone else's direction.
I think that is a very strange conclusion to jump to.
I'm not sure if I agree on the age thing. Yes, it would be difficult to hire a 16 year old for legal and reliability issues, that's why they should put up their age so that people don't send them irrelevant work inquiries. I started when I was 14, and I always tried to put my age somewhere it can be easily seen, so that companies intending to relocate me, or offer huge contracts thinking I'm 30 years old would go somewhere else. I think it's good to be upfront about these stuff.