How about following the definition you yourself picked?

>Although not a requirement, most good quality blogs are interactive, allowing visitors to leave comments and even message each other via GUI widgets on the blogs, and it is this interactivity that distinguishes them from other static websites.

Even with a reference to an academic paper and exactly what i said prior.

> You can't say that a "normal" blog has comments without defining those, you can't even define "normal" without defining the set.

I define the set. Easily. Take every site on this internet someone thinks is a blog and merge them to a default. You will have comments and ping/trackbacks (and PHP, probably).

You choosed an interesting example: Jekyll. There is that interesting motion that you can observe technical development to follow circles. Those new static site generators are on such a backward circle. As I was told, in those early times before Wordpress, it was common to use systems like this to generate the sites that resembled modern blogs. Then came Wordpress & Co, PHP-based dynamic blog-engines. With comments and ping/trackbacks. I'm pretty sure, like the wikipedia-entry you cited, there are enough definitions acknowledging that.

They became the archetypical implementation of a Blog for many years, just like the iPad clinges to the archetypical implementation of a tablet laid down by Star Trek and functional requirements.

The movement now to generate blogs as static sites is probably a reaction to the awful caching and ressource-usage of Wordpress or a reaction to the popularity of git.

> You use the term need, but imply want. Your blog has no commenting requisite, ...

Really not true. If I didn't have comments, my blog would almost certainly not exist anymore. Which qualifies as a need over a want.

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

There are people sitting on a tree claiming to ride a horse. Gruber for example is so popular that almost every entry of his gets dicussed here. HN is his comment-area. And no, that doesn't refute my own argument that a typical blog has a comment-area, because he has one (HN) and the unknown average Blogger has one on its site, or he gets no discussion at all, making him an atypical pseudo-blogger.

> Plus, comments and all of the ping/trackbacks 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?

Yep, they don't follow the typical blog-design. Though you can of course have trackbacks with plain-file-blogs without a dedicated database. I assume you included that with "some form of database".

And careful with the generic serverpart required: pingbacks use a generic and stadnardized xmlrpc-call, trackbacks are nothing but a POST with defined parameters. Sure, additional work to implement, but that is true for everything you really do with a server.

----

Again: Depending on when you started coming in contact with blogs, and I argue still today, it is highly likely that almost every blog you visit has comments (sometimes deactivated, nonetheless the engine has them), has some form of ping/trackback-machanism. It is so common for a blog to have those mechanisms that they became essential for the distinguishing between a static site with constant updates and websites we call blogs.