jq '.comments[] | {comment:{url_slug:.post.url_slug, post_id:.post.id}}'
{
"comment": {
"url_slug": "post-solar-system",
"post_id": 555555
}
{
"comment": {
"url_slug": "post-solar-system",
"post_id": 555555
"full_url": "https://экзампл.ком/post-solar-system-555555/"
}