Dana said: "Maybe canon gives us enough information about Avon's character to be intriguing, but leaves enough gaps to launch a thousand fanfics"
This i believe is key. There are so many takes on his character, mental stability and so on, that can come out of canon. Most interpretations can be backed up by what we see, which gives plenty of room for almost any fanfic interpretation.
The fact that loads of female fans fancied the pants off him also helps.
-- cheers Steve Rogerson http://homepages.poptel.org.uk/steve.rogerson
Redemption 03, 21-23 February 2003, Ashford, Kent Celebrating 25 years of Blake's 7 and 10 years of Babylon 5 http://www.smof.com/redemption