In reply to.
Or scrobbles. I “scrobble” my “listens” to my site rather than Last.fm. But I would not want my scrobbles to end up in there with my posts, notes, and everything. (I don’t care if “under the hood” they still end up in WP’s
wp_posts table. I do not want them messing up my “Posts” screen.)
Why I use CPTs, then, and not taxonomies? I have previously used Post Formats, and found it hard to—inside WP Admin—find things in that big list of posts that would house literally everything, posts, asides, quotes, links, and more.