When creating or customising sub-headings at a master level there is now the option to add further detail (as in further instructions of explanatory paragraph) and links to standards (the same as is possible on individual work-items).

Headings themselves are limited to 256 characters, whereas the text-box is unlimited. For example: 

Adding an underscore on either side will put the text into italics (just as using asterisks will bold text).

Once saved the heading will look like this: 

Existing sub-headings may be amended at the master level to include extra detail as above.