Yes, it is: right at the bottom, it adds a new line. But because it is blank, you can't see it, or tell it is there unless you move the input cursor to the end of the RichTextBox. Try this:
private void button1_Click(object sender, EventArgs e)
{
richTextBox1.Text += "Hello" + "\n";
}
private void button2_Click(object sender, EventArgs e)
{
richTextBox1.Text += "\n" + "Hello";
}
And you will see what I mean.