Laravel Eloquent Query Builder Puzzle

# Schema:
Post hasMany Threads
Thread hasMany Comments

# Problem
In this made up example, I'm selecting all posts, threads and comments that
have comments by a particular user. I'm not interested in the other threads, or
the other comments, just the Post data, Thread data and Comments for comments by
this user. In SQL this is easy:

SELECT
    *
FROM
    `posts`
    INNER JOIN `threads` ON `threads.post_id` = `posts.id`
    INNER JOIN `comments` ON `comments.thread_id` = `threads.id`;
WHERE
    `comments.user_id` = ?


How can I do this using the Eloquent query builder such that
when converted to JSON the results are properly nested.

Thee following is close:

    $qry = Post
        ::with(['threads' => function ($query) use ($id) {
            $query->with(['threadComments' => function ($query) use ($id) {
                return $query->where('comment_id', $id);
            }]);
        }])
        ->whereHas('threads', function ($query) use ($id) {
            $query->whereHas('threadComments', function ($query) use ($id) {
                $query->where('comment_id', $id);
            });
        })
        ->get();

But this returns all threads (rather than just threads containing
comments by the user) for the posts.