Weird comments

I get quite a few anonymous comments to random posts. They are random in that there is no apparent correlation between the content of my posts and their comments.

Examples:

Anonymous has left a new comment on your post "The trouble over inclusive fitness theory and euso...":

I think this is among the most vital info for me. And i am satisfied reading your article. However should remark on some general issues, The website style is perfect, the articles is in reality excellent : D. Good activity, cheers Here is my webpage :: the 2012

Anonymous has left a new comment on your post "Carnival of Evolution statistics":

Thank you for every other informative web site. The place else may just I get that type of info written in such a perfect manner? I have a mission that I'm just now operating on, and I've been on the look out for such information. My blog post ... Movie Maker Forums

Clearly the point is to promote some site (yes, I have changed the links). But why these robotish comment with no relevance to my blog posts?

None of these comments ever get through, because I moderate submitted comments to posts over a week old. And when they do get through to newer posts, they always delete them themselves right away. Why?

I really wish I knew.