Semantics, you might've read me discussing it somewhere else but this topic is different. Here, the topic's focus is about the intended use of HTML elements, rather than the linked-data semantics I've discussed elsewhere. Aside from the spec there are many articles, guides and debates online already, so I'm not reposting here. I just wanted to share some insights with the folks building these templates.
Most folks know that with HTML5 we got some new semantic elements, but few seem to know we had some old ones, as well; in fact, nearly every element has an intended purpose except for a few that are intentionally generic, i.e., <div>, <span> and for the most part <b>.
Check this out, btw: https://madebymike.com.au/html5-periodic-table/
Anyway, as for that insight i mentioned.
First of all, Heading Tags, make sure you're using them right, they should reflect the outline of the document (also i noticed use of a heading tag where a <header>+<h#> should have been).
Secondly, <time>. ALL dates* should be in a <time> element with a machinable value in the datetime attribute.
(* <meta> is also an acceptable element for (hidden) dates in some situations --like in a page's <head>. If <meta>, the content attribute's value should follow the same pattern as the datetime attributes.)
Valid Date/Time Formats
<time datetime="2017-05-22T17:20:41-0400">May 22, 2017, 05:20:41 PM</time>
or
<time datetime="2017-05-22">May 22, 2017</time>
or
<time datetime="2017-05">May 2017</time>
or
<time datetime="2017">2017</time>
or meta
<meta name="date" content="2017-05-22T17:20:41-0400" />
or
<meta name="date" content="2017" />
Thirdly, I've seen a lot of use of <span> or <div> where there should be a <p> instead.
Fourthly, <img> alt values, it's counter-productive to accessibility to leave them blank, especially since you have ARIA attributes added to the templates.
If it's a user-posted or linked pic, inform the alt attribute of that, if it's an icon, alt it so.
EDIT 4-b: re:ARIA. ARIA overwrites the semantic value of the element it's applied to, keep this in mind. --I haven't checked for correctness yet, btw.
Fifthly, never forget, the W3C's HTML Validator is your friend, the kind of friend that tells you when you're screwing up. I think i've only found one depreciated attribute in the templates, there was a name attribute on an anchor (<a>).
Lastly, the new semantic elements. I'm going to take a hard look at all the pages and figure this out, but a few points i wanted to make here.
<article> an article is a piece of data which can be understood solely by itself, so, a comment wouldn't fit this use since it relies on another piece of data being understood.
<section> defines a section of a document, yet has no hierarchical value, intentionally.
So this nesting indicates the <section> is part of a "complete thought".
<article>
<section>
</section>
<section>
</section>
</article>
and this use of a <section> means something different:
<section>
<article>
</article>
<article>
</article>
</section>
The proper use depends on the context.
More on all this later, just getting the topic started.