Seems like I wasn't paying close enough attention to the classes and their locations. Here's what I ended up with:
driver.findElement(By.className("yj-auto-width-fake-textarea")).click();
driver.findElement(By.className("yj-tapf-textarea")).sendKeys(Text);
driver.findElement(By.id("yj-yam.ui.publisher.old.SubmitButton")).click();