Comments are essential part of any blog. It provides an option to communicate with your blog visitors in easy manner, that is why it should be more interactive and hassle free. WordPress itself provides comment system but that is not social media enabled. I am providing here some best wordpress plugin from wordpress repositary which you can use in your blog.
Disqus pronounced as “Discuss” is best plugin available for wordpress or any other website which using commenting system for user communication. Disqus use their own api which prevent your blog from spammer. this is also integrate your wordpress blog commenting system with disqus user interface. You can easily manage comment from wordpress dashboard.
Subscribe to comment is another great plugin for wordpress blogger which is simply add a checkbox to comment system of wordpress. User can be notified whenever a comment added to a post.
Facebook provides one centralized plugin for all facebook feature. facebook commenting system is one of them. when you add facebook to your blog it over ride your comment system and allow user to comment using their facebook account which is also visible on their wall. It is best way to socialize your page.
OpenID is another standard which authenticate user without registering on your website. This also provide an option to authenticate user before making comment on your blog. you can always track that user. This enable user to login into your blog using their own wordpress.com account.
Comment spamming is a worldwide issue after introduction of blogging platform like wordpress. People do commenting on do follow blog to get a backlink which increase their page ranking in google page ranking system.
This is where Akismet helps you to avoid such spammer. it checks database for any malicious comment and mark it as spam if it contains any malicious link and you avoid yourself from being bombard by emails. Akismet is shipped with wordpress installation so you need to just active this plugin and add your akismet key on configuration page.
In conclusion, what plugin best for you depends on your use but I think that these are the Top 5 comment plugins for wordpress. If you think that you have any other wordpress plugin which should come into this list then you can leave that name below.