Yeah, I know, lots of things, but this specific thing is incredibly stupid.
Whenever a Blogger user posts a comment on another Blogger site, their username at the top of their comment is a link to their user profile, rather than their blog. When you go to the profile, there is no way to get to that particular user's blog from there.
So, essentially, you may see a really great comment and say, "Boy, I'd sure like to see what else he/she has to say." Sorry, you just can't do it.