If attribute "content" in meta tag contains comma or semicolon, for example:

<meta name="author" content="Foo, Foo"/>

then quotes appears in PDF description.

You're right! But why? Checking the actual contents of the PDF file shows that no quotes are present:

/Author (Foo, Foo)

But Acrobat displays it with quotes when it contains a comma, I'm not sure why.

I'm sorry; obviously the problem is in Acrobat Reader 9 - version 7 displays text without quotes.