If you comment on any article in this blog more than a couple of weeks old, it goes into an "approval" queue which I check and process 3-4 times a week.
I often find that, combined with some useful comments, a few spam messages. Over the last month or so I've suddenly found these spam messages have been written in such a way that they sound quite credible! Indeed I approved one of them until it suddenly dawned on me that it was a little strange and had to go back through all the comments to remove it.
Some spam-merchant, somewhere, has actually sat down and thought about a few general flattering responses that could be applied to any blog, even if the English is less than perefect. The only clue that it is true spam is that, at the foot of the response, a link to a web site which has (I assume) paid for the spam. This is itself disguised as one short word (I don't see the URL unless I hover my mouse over it).
Here are some examples (viagra and fake rolex links removed, sorry):