House Choice doesn't Equal Personality for Life

[Jen Reese]

No: HPFGUIDX 85224

On several different threads I've seen comments about how someone 
couldn't be evil because they were in Gryffindor, or that person 
*is* evil so they must have been in Slytherin.

Why does the Sorting Hat decision at age 11 mean you will have those 
characteristics your entire life? Personally, I'd like to find out 
MWPP were in Slytherin or someone from Gryffindor is a betrayer. 
Meaning all the houses have postitive and negative characteristics, 
and that being in a certain house doesn't predetermine your entire 
existence. 

It is canon that there were a group of Slytherins in the MWPP era 
who all became DE's, but that seems to be the extent of 
generalizations we can make about a group of students in one house 
(correct me if I'm wrong).