Flood of long (semi) related, suspicious comments to my blog posts.

This week I have noticed an influx of comments on my family oriented blog. They are clearly written by the same person (or a group of people) as they appear within 1-2 hours and then stop. This would be obviously a sign of a spam, but there are no links in them.

Also, they are all fairly long and many of them are actually very much related to the topic but then there are some, that are totally off topic.

Also, many of the comments seem to be unique, but some are exact copies of text from other websites.

And websites the author(s) link to are a variety of Facebook profiles. These are not links inside the comments, but just regular links that user submit along with their email address and name.

Each of the Facebook profiles is private, I cannot view the wall or anything about the person behind the profile (and there are no profile images either).

Anyone experienced these type of comments? And what's the purpose of submitting them?

BTW, I hold all comments for moderation so none of them was actually published, yet they just keep coming.

But if there's no link.... is it maybe some black hat tactic to get my site penalized? Or maybe a hacking attempt?

I know, I may be a bit paranoid, but I just don't understand the reason and purpose of these comments. Any ideas?