The process is called Silver Nitride on the receiver, but it is called "silver" because of the color left behind: nitrided steel may be "silver" coloured but there is no silver metal involved in the process. Nitriding is a very hard surface treatment for steel. If effectively done, it is very unlikely to get scratched. It is also too hard to polish with domestic products.
This leaves two issues:
1. It won't be easy to dull and you will need a very hard abrasive to do it... and to not leave scratches you will need a very fine abrasive.
and
2. You are actually removing a surface coating that is the firearm's defense against moisture, corrosion and the elements as Browning states their receiver is a form of "standard" steel and not "stainless" steel with the Nitride coating.
The above is a summary of looking at Browning's own site and a couple of articles/posts on removing scratches in the Cynergy composite receiver.