A "normal blog"? That requires that one define normal, with a set of metrics, it also requires a set of websites to be analyzed. Should that set be all blogs hosted with WordPress or Blogger than yes, normal becomes having comments, because that's the default option.

But, if you use a different set, say a group of people who use Jekyll or another static site generator, than normal turns into no comments.

Do we include all sites that consider themselves to be a blog inside of this set? Should there be a number of readers over time and a number of posts over time requirement? Should the content being delivered be of a certain category? You can't say that a "normal" blog has comments without defining those, you can't even define "normal" without defining the set.

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Definitionally, a blog does not require a commenting system. I said it before, and you seem to be refuting that. [Wikipedia says that](http://en.wikipedia.org/wiki/Blog)

> Although not a requirement [...] blogs are interactive, allowing visitors to leave comments

Yes, I took out the "most good quality" part, because it shows a bias.

Princeton WordNet defines a blog as "a shared on-line journal where people can post diary entries about their personal experiences and hobbies", making no reference to comments at all. The Wiktionary also has no references to comments. [WordPress' Codex](http://codex.wordpress.org/Glossary#Blog) likewise makes no reference to comments inside of it's blog definition. Same with [Blogger](https://www.blogger.com/tour_start.g).

There are many people called bloggers who's sites don't have comments, Gruber's Daring Fireball, Marco Arment's blog for a few.

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You just proved my point about nobody needing comments. You use the term need, but imply want. Your blog has no commenting requisite, you just enjoy having them. Functionally it would have very few differences if it didn't have comments.

And, I never said nobody wants comments. There are many instances where people may have a site built like a blog where comments are meant to be a discussion board of sorts where some BBS for forum software would suit them better. There's no commenting requirement for a blog to be a blog.

Some people may enjoy discussion inside of a comments section of a blog, and some people may operate their website in a manner dependent on a comments section, but I would argue that in such cases they're the ones who aren't operating a "normal blog", and are instead operating a discussion forum of sorts.

Likewise, trackbacks, pingbacks, and refbacks are not required for a blog either. None of those are official "web features" as specified by the W3C or the WHATWG the two organizations considered to be the "keepers of web standards". And it requires additional work by the publisher as it isn't something that can be implemented by generic server software (note the generic part, server software created specifically for serving a specific piece of software could very easily implement them).

Plus, comments and all of the *backs require some form of a database to run, even if it isn't your own database. Are you saying that a database is also a requisite for a site being considered a blog?