It is a common thing that if you have some login that creates the
title element content to finish with several new lines in it. For example:
<title> Title | Category | My Site Name </title>
Does this has some semantic falls? Is it bad for SEO?
New lines do not affect SEO. That won't hurt you at all.
Search engines mostly ignore whitespaces in HTML code so this should definitely not affect SEO.
I would say NO, because if they do affect SEO it means that Google sees differently also:
<p>hello babe</p> <p> hello babe </p>
which are exactly the same thing and are rendered exactly in the same way by any browsers.
No, it won't affect your SEO, Amit is right: Google ignores whitespace as many designers are not aware of structuring HTML, Google understands the fact well, but - maybe in future it will.
What I would like to ask you is why you are going to do that. I don't think you are going to be benefited in any aspect by doing so.
No, though if it's doing something like this throughout the code it could create a small amount of drag because of the extra whitespace. You may want to investigate minifying your code.