No - even if they choose 'yes', you cannot bring up their E mail address by clicking on their name in a post they wrote. You can only reach their E mail (via their 'Profile') when you see their name in an index - such as on the main 'Discussions' page, or the list of all the threads within a section. It's quite odd - and rather impractical - that it's arranged this way.
So, while it's not really a loss of a function (it's more like a loss of half a function), it is a loss of practicality. Not being able to adjust the size of the very tiny font through IE settings IS the loss of a function - a rather significant function. As I re-read what I'm typing here, I can't tell the periods from the commas, everything is so bloody small.