There is a bug where when copying text with multiple line breaks (new lines, carriage returns, etc.), and pasting it in the Rich Text Editor, the Rich Text Editor will remove the line breaks. Here is a GIF I created using Gifcam to capture to show you what is happening. I have linked it below to Gfycat. GFYCAT HTML5 version. GFYCAT GIF version. I used the Xenforo Test Forum to test the copy/paste issue, and it is apparently still in the current Xenforo.