I researched Bitacle, this is from their FAQ. It is unclear what it means, and is probably written by a non-English speaker. One thing that is clear, they get the articles from RSS Feeds (which you can limit or disable in WP, but it's turned on by default). Here's the info I found:
What type of blogs are inlcuded in the search?
All blogs that has a feed. This it can be RSS or Atom.
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How I can do that my blog appears in the list?
If your blog publishes a feed in the web (in any format) and automatically makes ping to a service of updates, like, for exampleWeblogs.com or Feedshot, we can find you and add it to the list.
What happens if I don’t wish to appear in the list?
If you doesn’t publish feed, it won’t be included in the blog’s search. Nevertheless, if you previously has published feed of the site that was indexed, the old entrances will remain in the index, although the new ones aren’t added.
The blog search don’t follow the archives ‘robots.txt’ or META labels like NOINDEX, NOFOLLOW.
I don't know what that last sentence means, when it says "The blog search don’t follow the archives ‘robots.txt’ or META labels like NOINDEX, NOFOLLOW." Does it mean these methods will preclude Bitacle, or these methods have no effect on Bitacle?