I'm not quite sure what you mean, but I'll try to give you a solution anyway.
If there is a post you want to reply to, you can reply to a specific part of it, or all of it. If you highlight the text you want to reply to, a button should appear saying "quote reply" or something similar. If you click that, then type your reply, it'll show up that you're replying to that specific post.
At least it's only minor.
If that's not what you mean, please let me know!