This feature is seriously broken, when I try to paste the tab from text editor into the textbox, new HTML editor decides to play smartass and interpret what I wanted to do in its own mixed up way. No matter how much I tried I couldn't get it to stop screwing up with line breaks, even when I edited HTML manually. Please, remove this novelty altogether, it is more trouble than it's worth, the old text box where you could old fashionably paste as plain text was working without glitches.
This problem is dues to the fact that the page needs to be rendered different if it was the old version or the new version. You tab did not have any of the identifiers I have been using so I added a new one that your tab did have. This is going to happen once in a while as long as we want to support both formats (which will most likely be forever).
At first when I edited it, it turned out a mess so later I changed it to a different format to see what it would do. It seems to have fixed it but I still had to get the numbers lined back up with the words. I guess the problem is more with the auto formatting.