Why? I know that it's not best practice, but I don't see the point. If one does that, so be it.
Doesn't break your website, doesn't safe you bandwidth.
Remove all unnecessary and unwanted comments from your HTML
An example would be nice. What exactly IS unnecessary and unwanted?
The currency symbol for the Euro is &eur;.
The currency symbol for the Euro is "".
Can someone explain this to me? Doesn't make much sense. Also, it's € not &eur;
Isn't a big focus of HTML5 to add more semantic meaning? Why would you then omit something that adds it? Even if it's unnecessary?
HTML5 isn't even finished. What if they change that in the future?
It doesn't harm your website, so keep it.
That's your formatting style, not mine.
Also: new lines are 2 bytes big
My suggestion: Read some best practices but see them as recommendations not as strict rules. Use what you are comfortable with. When it makes sense to you, use it.
Don't go byte hunting. It's not really worth the effort, except your site has huge traffic and you need to cut some bandwidth.