I don’t know if this blog is necessarily out of my niche, but I did comment on it because I felt rather strongly about what the person was trying to say (or what I believed she was trying to say). I was only the second person to comment on the blog, the first comment was a stock “Your posts are awesome. I love them all!” Which is great but doesn’t necessarily reflect any interaction between the blogger and the bloggee (?). So far, the blogger has not responded to my comment, but that’s ok. Sometimes people choose not to engage and simply want to put their opinions out there for others to see.
But I think if you’re going put a challenging opinion out there, you should be ready to discuss and/or defend.