Would You like to revise this issue? It seems to be inconsistent.

# |Why deriving from "Class" class is denied?
# 
# In a mail on 1998-07-15, I wrote that "it (subclass of Class) 
# would not work properly due to the limitation of 
# implementation".  So, that was the reason.
# 
# To tell the truth, I don't remember what exactly was the 
# "limitation". 
#