WP Most Popular is a simple plugin which tracks your most popular blog posts based on views and lets you display them in your theme or blog sidebar.
99% of the time this is because no posts have been visited yet to receive a ranking. Simply click on a blog post to read it on your blog and it will receive a ranking and display in the list of most popular posts.
Yes, please do so on the WordPress support forum for the plugin. I will consider it and if I feel it is worth adding, I will schedule it for a future release.
Yes! The plugin is open source and I host it on Github. Feel free to send me pull requests.