Boofo: if you don't know who said a certain quote, use
Unknown
as the name, and
U
as the letter.
(and later on, if you find out who said the quote, you edit it again

)
And no, if you don't enter a Letter, those quotes won't be listed at all in the letter-specific index, in the Quotes List hack. They will only display in your header (or wherever you've placed them) and in the Quotes List when searching, or looking at it in default view. But not when browsing the list through letters, so you really ought to set a Letter entry for EVERY quote in your database.
Consistency is the key to success