Can your web site ranking be affected if many pages are in Google Supplemental? Do I need to work on removing the links from the supplemental results by tweaking robots.txt on my site (restricting googlebot from some links)? And if so, what approach should work for a Wordpress blog? Thank you!
From my own experience having a few hundred pages in supplemental results won't hurt your overall rankings that bad. But still you should tweak your robots.txt file. WordPress is known to have such a problems.
supplemental results are the pages which have lost quality for a temp. time. blocking your supp. pages will not help you. google does not convert them to the normal index. you need more backlink for your supp. pages