5 minutes ago I have written a post with a Github Gist. You can embed Gists like this in your posts
<script src="https://gist.github.com/GordonLesti/8822532.js"></script>
But the gist has looked like this
The problem was a css conflict with the Twenty Fifteen theme from WordPress and the css of the gist. You can solve this problem with the following code
<style>
.file-data table {table-layout: auto;}
</style>
<script src="https://gist.github.com/GordonLesti/8822532.js"></script>
And the Gist will look normal again