CSS selector to separate posts by current user

Development
8

After digging a bit in plugin-api I think I found solution to your problem and the proper way of doing what you suggested

<script type="text/discourse-plugin" version="0.8">
  api.addPostClassesCallback((attrs) => {
    const user = api.getCurrentUser();
    if (attrs.user_id === user.id)  {
      return ['current-user-post']
    }
  });
</script>

Check here:
https://github.com/discourse/discourse/blob/master/app/assets/javascripts/discourse/lib/plugin-api.js#L712

This will add current-user-post to every post that is made by a current logged in user.