Although I hasn’t confirmed this with some scientifically acceptable experiments, it seems like commenting systems in blog such as WordPress based sites are rejecting Windows Live Profile URL as spam. I used to post comments using the Live Profile ID (cut and paste of course, because I’m not the type that enjoy memorizing pi number outside my head).
http://cid-280a1538334a1cb9.profile.live.com/ <== my Live Profile URL
Well… understandable. Normally, peoples don’t make ID with 16 digit seemingly random hexadecimal value for their URL. The only thing that use e-mail address or domain name with random characters are spam bots. So logically, they’re rejected as spam until moderated.