Summerwind,
All you have to do is look to the bottom of my post on the right side and it will say:

(in reply to: xxxxx)

That's how you know who a person is addressing.

I don't always scroll to the bottom of the page and hit the reply button. You can reply to any person in the discussion by hitting the reply button at the top of their post. WHO you are replying to is indicated on the bottom right side of your post.