Hey dude, I coincidentally entered your profile, and though I had nothing special to say I thought I'd drop a comment, seeing that you apparently never understood how to use the VM* system correctly.
Since I'm a nice guy, I decided to tell you, so you would not continue make the same mistake forever. Whenever someone writes at your profile, their comment appears in this list of comments forever, unless you delete them, or the writer does.
Back to the point - if you want to reply, you will have to go to their profile, by clicking on their name or picture, or press "view conversation". Your message must be written either on their user profile or in your shared conversation (This will appear on their profiles too). So far, you've answered them, on your own user profile, which will not notify them in any way, and people seeing it will think of you as a crazy man talking to himself
Hopefully it helped
*=Visitor Messaging (Writing on other users' profiles, like I just did)