Something has changed with the styling of HTMLEditor in 8u20. It used to look good inside a TitledPane, but now there's extra spacing or padding added around the toolbars. Here's a really simple example:

https://gist.github.com/ryanjaeb/683e782e7a6343319afb

Run the above with 8u20 (b15) and the extra padding will be immediately noticeable.