MC nfo files use the XBMC standard as default, the nfo files are fully supported and can be imported by XBMC.
Rescraping replaces the contents of the field with the rescraped contents.
eg
<rating>5.1</rating>
when rating is updated will change to the current rating
<rating>5.2</rating>.
The whole file is resaved, but only altered items will change.
Currently MC supports all XBMC tags.