Happy new year everyone. I guess I'm ringing in 2018 with a bug report. 😉
If you create a form section HTML cell and you try to "<<...>>" in the label, all you get is "<>:".
My lazy workaround is to hide the label and do this in the HTML:
<b><<BO.LabelAttribute>>:</b><p><p>
<<BO.ValueAttribute>>
The spacing between the label and value isn't quite right though (but better than if you just use one <p>).