There are few plugins that may be worth of money you invest in for your blog. CommentLuv is one of those plugin that will help you to build a successful blog, with loads of features for you and your readers. It helps you to to build social interaction and promote your content that will help you to build traffic for your blog and build your blog community. It helps in preventing spam and encourage social sharing. On other hand, reader gets backlink benefit when they link their content on your blog giving them loads of link juice with an anchor text.