Hi Martin,
the answer to quiz question 1. (Do you consider icons to be) is c :
c) styling / usability aids
Icons cannot benefit accessibility, but when used correctly can benefit usability and make things look pretty.
I know from previous posts there is a great deal of confusion about the terms accessibility and usability with the two being used together and interchangeably on the forums by many people, so i'll set out the difference between accessibility and usability.
Web accessibility
designing for accessibility on the web means enabling users with :
- Visual impairment ( poor eyesight, color blindness, blindness)
- Motor/Mobility difficulties
- Hearing problems
- Other difficulties
If are using a screen reader you should not have to be read out anything (alt, title or src) about a decorative image - the link text itself is all you want to know about. An inline icon is just another dom element you have to navigate past to get where you want.
It your turning off css, there is probably a good reason - decorative inline icons will be an impairment rather than useful to you.
Decorative icons do not need the accessibility standards you would apply to images which provide content. Trying to make any decorative icon accessible (e.g. title, alt etc) is just adding noise.
You would as likely put a title and alt tag on a rounded corner as you would a decorative icon.
Web usability
designing for usability of the web means enabling all users.
- Presenting information to the user in a clear and concise way
- Give the correct choices to the users in an obvious way
- Remove ambiguity regarding the consequences of an action
- Place important items in an appropriate area on a web page or a web application
(yeh, that list is from wikipedia 
Icons exist on the web to make things look nice and aid usability.
Hope this helps
Stuart