Yup, I would hesitate to use anything abrasive on anodized or electroplated plated gunwales. The “Flitz Polish” that FurtherNorth used on her anodized gunwales seemed to do a good job without marring the anodization.
I used Burnishine Aluminum Brightener from West Marine for plain aluminum gunwales. That is by instructions a “paint on and rinse off” product. For one set of uncoated aluminum gunwales on a left-in-the-dirt canoe I had to use a Scotch-brite pad to remove the years of crud, and that abrasive action left a dull matt finish, which I kinda preferred to bright and shiny. I did put marine wax on those gunwales so the micro-scratches didn’t become dirt magnets.
The Burnishine contains “Acids and Flourides”; I have no idea if that would eat into anodized or plated gunwales.
The Fritz polish is a more expensive than a 16oz bottle of Burnishine, but it doesn’t take much to clean a pair of gunwales.