As others are saying the content is great! I echo the other praises. Only gripe I have @harrydry is how the posts load in a popup modal. I find it pretty difficult to read posts because of this.
If you don't feel like changing too much, I found changing the width value of .post from "80em" to "80%" helps a lot (then maybe add a min-width value). In addition, changing the .outerPost background value to "rgba(0, 0, 0, 0.6)" improved it a lot as well. You'll find it's a more standardized look to contentful modals, very similar to the one used right here on ProductHunt!
Of course, this is all unsolicited advice and you can feel free to ignore it! Although I suggest giving it a try and deciding whether you like it or not ;-)
Again, props on the creation and I wish you luck 🙂