When you reply to someone's post, your replies are visible beneath the original post. If you're followed by the blog, your reply will be immediately approved and visible. If you're not followed by the blog, your reply will default to pending, which requires an extra click to view.
Your reply can be dismissed by the post's author or blog's admins, which will remove it from the original post. If you're replying to a discussion threaded under the original post, the user you're replying to has the ability to dismiss your post as well.
Regardless of what state your reply is in, it will always be viewable on your profile.