Sounds like what you are saying is that the pin mark is in the middle of the rib detail. I've had similar problems as the one you are describing.
1. Sometimes the easiest thing to do is not to attack just the pin mark, but the whole rib detail. Try sanding down the rib to the point where the pin mark is gone, and build it up again using strip styrene (.005" or .010"). In many cases, the rib I replaced looked better (in my opinion) than the molded one. I just did this on Italeri's 1/35 M101 105mm Howitzer. The recuperator was terrible. I replaced the mounting ribs with sheet styrene; turned out better than the original kit molds.
2. Try drilling into the pin mark then cut a piece of styrene rod the size of the hole and cement in place. When dry, cut the rod flush with the rib, and finish accordingly.
3. MicroMark ( www.micromark.com ) makes a seam scraper tool that may be able to help get into the area that is inaccessible with your #11 blade. If you try to repair it that way there's still going to be some sort of indentation/valley left where you scraped plastic away that's still going to have to be blended into surrounding detail.
4. Lastly, try filling with putty or superglue and sanding, if you can get a piece of sandpaper in that location.
Well, there's 4 options. Hope one of them helps a little.... Good luck!
Gip Winecoff