SEO Blog Comments - What the SEO specialist uses

What blog comment system do the leading SEO specialists use?

So here is an experiment. I searched for "seo blog" and looked at the top 10 sites to see what they do. Maybe we can learn something from SEO blog comments.

Moz

  • Using a custom comment system.

SEOBook

  • You have to log in to find out. I haven't bothered as yet.

SeoNick

  • WordPress comments with a "NOT a spammer" checkbox. Seems to be provided by OneAll Social Login WordPress plugin. A social login service which has a free tier and different pricing tiers.

SearchEngineLand

  • Disqus WordPress Plugin

BlogTyrant

  • Looks like it has standard comments, but there does not seem to be a way to comment as an anonymous user. I can't see anywhere mentioning you need to log in, but maybe you can comment if you do.

Inc

  • They seem to have their own commenting system.

SearchEngineWatch

  • Disqus

GravitateDesign

  • Standard comment system

Number 9 was Support at Google for Blogger which has no comments

Blog HubSpot

  • Custom comment system? So they are using mainly local comment systems, rather than a third party comment system like Facebook or Disqus.

I remember reading blog posts about this and a few bloggers seemed to be moving away from systems like Disqus and back to their own WordPress comments.