Manufacturer markings on new boards -- how do I get rid of them?

We recently replaced all of the horizontal boards with very nice treated pine boards which theoretically require no sanding before we stain.  They look great, but they have a lot of manufacturer's markings.  [While we're at it, any idea why the manufacturers do this -- it just makes our job harder?]

We'd like to do a semi-transparent stain, but don't like the idea of seeing the manufacturer's name, lot number, etc. forever.  I suppose we could sand, but that's a lot of sanding.  We tried a couple of cleaners on extra pieces of lumber, but they helped very little.  Oxygenated bleach was recommended, but didn't seem to do very much.

I tried to attach a picture, but all I got was this:

We have about a 500 sq ft. of deck (actually two decks separated by a screened in porch).  Most of deck gets direct sunlight, but two corners get very little and are prone to some mildew.