Sometimes I come across blog comments that are just a bit too generic. They’re complimentary, but don’t mention anything specific to the topic of the post. When this happens, there is a good chance the comment is a piece of spam.
Here’s an example:

It’s certainly polite, although it also says nothing related to the topic.
Other hints: Keyword stuffed username, SEO site, and an email address a human would never use (test@)
If that wasn’t enough, I searched for the blog post’s phrase on Google and found this:

WOW! That 10-word sentence has been indexed 17,300 times by Google.
Looks like that spammer has had quite a bit of success getting their spammy comment past thousands of bloggers.