Comment spam is an ongoing problem for most bloggers. I've had my struggles with it over the years, but I've largely got it under control.
My biggest kind of comment spam these days comes in asian characters that I don't understand. I don't want to be a jerk and delete all comments in a language that I don't understand, but I also have a strong suspicion that this is spam.
I have found that 90%+ of all comment spam is on posts that are 90 days or older. These old posts have serious google juice and are great honeypots of traffic (and spam). So when I see stuff like this on old posts in a language I don't understand, I generally delete it.
It's a tricky problem for sure.