How Riddle Knew He Was A Descendant of Slytherin (WAS: Heir defined)

[Phyllis]

No: HPFGUIDX 58835

In response to my ponderings about how Voldemort would have found out 
that he was a descendant of Slytherin, Innermurk suggested:

> Here's an idea, what if the Sorting Hat told him? 

Me again:

I actually did consider that option, especially in light of JKR's 
statement that there's more to the Sorting Hat than meets the eye.  
However, what gave me pause was the fact that the Sorting Hat was 
once Godric Gryffindor's hat, and given the enmity between Gryffindor 
and Slytherin, I suspect the Hat would not have divulged Riddle's 
Slytherin ancestry to him (assuming the Hat knew about it in the 
first place, that is).  Also, it's the Sorting Hat that Fawkes brings 
to Harry's aid in the Chamber when Harry is fighting against both 
Memory!Riddle and Slytherin's serpent, so I really see the Hat as 
being part of the fight against the evil Slythierin and Voldemort 
represent.

~Phyllis