Why these odd anonymous comments?

I've been getting comments on my blog (hosted by blogger) that puzzle me.

• You have brought up a very wonderful details, thanks for the post
• Appreciate it for helping out, excellent info
• This site definitely has all the information I needed about this subject and didn't know who to ask.
• Hi Dear, are you actually visiting this web page on a regular basis, if so afterward you will definitely obtain fastidious know-how.
• Excellent post. I was checking continuously this blog and I am impressed! Extremely helpful info particularly the last part :) I care for such information much. I was seeking this certain info for a very long time.  Thank you and best of luck.
• You have made some good points there. I checked on the web for additional information about the issue and found most individuals will go along with your views on this site.
• I am in fact pleased to glance at this webpage posts which contains lots of useful data, thanks for providing these kinds of statistics.

   
It wasn't until I had gotten 2 or 3 that I went from "Publish" to "Delete" to "Mark as spam" (the three options offered by blogger.)

The things that distinguish these comments:

• They exist. I rarely get comments. These happen once or twice a month 
• They always are Anonymous
• They always have bad english grammar.
• They don't fit any known category of spam; not promoting anything or links anywhere
• They are flattering
• They contain nothing that would associate them with the content of the blog post they are commenting on.

Here are some theories:

• This is a data communication method, using steganography based on grammatical or punctuation or word choices.
• There is some grad student running experiments / training an AI etc. based on human spam detection
• Someone is running a background check for blogs that auto-publish anonymous comments.

Any better theories? Leave a comment 😀