To me this feels like something GitHub would approve of. GitHub Issues intentionally gives users a lot of freedom so they can use it however they want. Unlike competitors who forced you to do something a certain way.
This is creative, and if your blog is hosted via GitHub Pages, then using Issues to discuss the content is not far-fetched at all.
Yes. I see a way GitHub could turn the Issue feature into a more flexible service that explicitly allows this kind of use cases. However, as of now, there was no explicit wording that encourages creative use of Issues and its API.
While GitHub may keep silent now as there are not many people doing this, if in the future the "hacks" become more popular, we could see GitHub taking a stance on this.
I certainly hope GitHub can gives some explicit consent to these use cases, which could lead to an entire set of new services that GitHub can offer (like what Google is doing currently).
I remember that when people started to use GitHub for other things besides code GitHub released a blog post telling it liked the idea, and started to display formatted CSV, YAML front-matter, GeoJSON, PDF and who knows what else.
This is creative, and if your blog is hosted via GitHub Pages, then using Issues to discuss the content is not far-fetched at all.