Bam! Fixed it. Make sure the discourseEmbedUrl is a full URL, not a relative path. E.g.:
var url="https://dev.bigsmall.io/articles/action-brands-are-important-urgent-credible/"
DiscourseEmbed = { discourseUrl: 'https://community.bigsmall.io/',
discourseEmbedUrl: url };
(function() {
var d = document.createElement('script'); d.type = 'text/javascript'; d.async = true;
d.src = DiscourseEmbed.discourseUrl + 'javascripts/embed.js';
(document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(d);
})();