Commento is a platform that you can embed in your website to allow your readers to add comments. It's reasonably fast lightweight. Supports markdown, import from Disqus, voting, automated spam detection, moderation tools, sticky comments, thread locking, OAuth login, single sign-on, and email notifications.
Most other products in this space do not respect your privacy; showing ads is their primary business model and that nearly always comes at the users' cost. Commento has no ads; you're the customer, not the product. While Commento is free software, in order to keep the service sustainable, the hosted cloud version is not offered free of cost. Commento is also orders of magnitude lighter than alternatives.
Read the documentation to get started.