No... NoFollow but they are going through a proxy/redirect which is the same as using nofollow. Besides that SE's don't have to play by the rules, they make the rules and give you an opportunity to get some free advertising. The above argument is a strawman argument that the lame and spammers hide behind to justify unethical and unprofessional conduct. SE's are not public entities! They are private so like you can do what you want on your site, they can do whatever they want because basically you are riding on their dime!

__________________
Follow me on Twitter! On the Trail with SOSG How I became a Social Media Convert and Twitter and Agents of Influence and now regular poster at Cloudmixer where We're Mixing New Media Ideas.