Member list reveals member information on click (#2)
this popped out at me, I haven't looked at the entire code completely yet, so take this with a grain of salt please

not sure why you do this

&lt;a href="#member-name-2" class="block-list__link"&gt;
   &lt;div class="block-list__thumbnail"&gt;
       &lt;img src="member-name-2-thumbnail.jpg" alt="Thumbnail"&gt;
   &lt;/div&gt;
   &lt;span class="block-list__title"&gt;Member Name 2&lt;/span&gt;
&lt;/a&gt;


I would probably write it like this instead

&lt;a href="member-name-2" class="block-list__link"&gt;
    &lt;img src="member-name-2-thumbnail.jpg" alt="Thumbnail" class="block-list__thumbnail" /&gt;
    &lt;span class="block-list__title"&gt;Member Name 2&lt;/span&gt;
&lt;/a&gt;


I am pretty sure that you don't need that extra div
I think the image tag is going to act similar to the div tag, and I assume that you want to style the image and not the div anyway,  it looks more like a container for the image which I think is redundant. ( I have been wrong before and am not afraid to admit it when someone gives me some solid evidence )

that is the only thing that I can see right now, but I haven't spent much time looking at it either.