So can the asteriks be more than two?

Answer 1

So, like:
/*** **/
?

Seems like it works to me...

Answer 2

** means exponentiation in some languages

Answer 3

After the first * in /* the compiler is looking for */ so
/************************************************************/
is completely legal and I've seen it used as marks to point out functions. With thousands of lines of code in a file, you need a quickly visible method to notice important details like that.