I like this, but maybe we can make it shorter by having more examples. Like:

    Of course, you can have more than one optional placeholder (e.g. ``/blog/{slug}/{page}``),
    but everything after an optional placeholder must be optional. For example, ``/{{page}}/blog``
    is a valid path, but ``page`` will always be required (i.e. simply ``/blog`` will not match
    this route).

What do you think? It's kind of a trick explanation, that needs to be done quickly.