I've not utilized commenting systems for blogs ( up until this one ) for a variety of reasons.
Primarly, these would be privacy & efficiency
As far as privacy goes, I have run my websites with a mind on preserving reader's privacy. I run Google Adsense ( on the knowledge that Google likely knows more about you than you do ) and Amazon ads, but as "opt in" adverts ( Amazon doesn't know you're reading this blog until you click the ad ).
I've always seen a blog as a way to impart information - not put on a hurly-gurly show with megabytes of fluff that dances around the actual words. I find mouseover effects & other visuals that have nothing to do with the content to be wasteful.
So, in the face of the above, I've always preferred a low-resource blog, and usually use a blog compiler ( which produces plain ol' HTML pages for maximum efficiency ). These blog compilers don't usaully facilitate a commenting system, and TBH, I've stayed away from adding a comment system for the following reasons . . .
If you're using Wordpress or some other hugely bloated blog software, you'll have a well-written ( and bloated ) commenting system that comes with it. If you're using plain ol' webpages, you'll need to find a third party solution
The biggest monkey on the swing would be Disqus ( they say it's pronounced "discuss", but I call it "disgust" ). Disqus offers both paid and free options, but as you know - nothing in life is free.
If you take Discus' "free candy", they'll disrupt your blog page layout with a huge rectangle of salacious clickbaity shite.
The above is a tame example of Disqus' ad units. Most of the time, the images are far more tabloid ( think "page 3 girls" ) and the text much more gossipy.
. . but that's not all . . .
However, a recent blog post revealed that every embedded Disqus frame made about 90 network requests increasing the load time by a full 4 seconds. It was discovered that they used tens of third-party tracking services on all pages.
So, using Disqus not only disrupts the page layout, but it makes the page load slower & tracks all the readers like animals.
So, this is why I don't use Disqus for comments
Facebook is another entity that'd love for you to use their commenting system. After all, F*c*book's users are its product. Yep, if you've been living in a cave for years, F*c*book exists to gather data on you so it can sell this data to marketing companies. They offer "Facebook Comments" for bloggers to implement into their blogs, because everywhere F*c*book has a spot on a webpage, that's just more internetizens they can surveill.
Couple of more facts from an old webmaster: F*c*book "like" buttons are the eye of Sauron ( they allow F*c*book to monitor everyone who visits a page with such a button ) and - most importantly - Facebook was designed to be addictive.
So, definitely no "F*c*book Comments" for this blogger.
There are quite a few third party & open source commenting systems out there, but their downfall is the lack of spam control. If I install a comment system, I don't want to spend more time cleaning up after spammers than writing blog content.
This blog is produced by the open source software bashblog, and bashblog comes with built-in twitter commenting. This is opt-in ( twitter knows nothing of this site until the reader clicks the "comment" link ). Twitter also has excellent anti-spam capabilities.