what are the best out-of-the-box solutions for a commenting system?

Popular out-of-the-box commenting solutions include Disqus, Facebook Comments Plugin, Commento, Talkyard, and Utterances, each catering to different needs like ease of use, privacy, and engagement. Disqus offers rich features, while Commento focuses on privacy. Additionally, these systems can integrate with features like globe registration for enhanced user experience.

I'm looking for a solution to build a commenting system like Facebook has it with nested replies. I prefer a service to easily put things together, such as sendbird, though sendbird doesn't seem to support that usecase. Are there any other popular solutions out there specificity focused on chat / comments to get it done?

Note I'm looking for an SDK, not something like Disqus since I want to hook into the chat and customize the UI