More on Nested Constructs

I revisited the Jeff Friedl expression today ( Matching Nested Contructs ) and I'm really starting to scratch my head.  Here's the pattern again:

text = @"before (nope (yes (here) okay) after"

pattern =
    @"\(
        (?>
            [^()]+
        |
            \( (?'DEPTH')
        |
            \) (?<-DEPTH>)
        )*
        (?(DEPTH)(?!))
    \)";

In the previous post, I admitted to having no idea what this line meant:

 (?(DEPTH)(?!))

It's a conditional evaluation statement (?(expr)yes[|no]) that is designed to fail the Match if the expr evaluates to true.  The (?!) part forces failure (refer Mastering Regex 2nd Editing page 333).  Here's a snippet which highlights this:

// Test one
string source = @"Darren" ;
string pattern = @"(?'MYTEST'Darren)" ;
Console.WriteLine( Regex.Match( source, pattern ).Groups["MYTEST"].Success ) ;
//Displays: True


// Test two - force failure
string source = @"Darren" ;
string pattern = @"(?'MYTEST'Darren)(?(MYTEST)(?!))" ;
Console.WriteLine( Regex.Match( source, pattern ).Groups["MYTEST"].Success ) ;
// Displays: False

My next goal is to understand why, given the following source and pattern, there is a Match but no text is consumed into Group 2:

source = "8 F 8 F ) 8 F ) ) "
pattern = "((8*)?)*"