I developed a mixer process and patents for CMP used in the semiconductor industry for polishing excess copper from the chips in a process called damscene. I designed mixing equipment to evenly distribute 0.125 micron abrasive particles in colloidal suspensions so that when they were poured over the copper and polished, the tiny imperfections were removed evenly. This process increases chip yield in the 300 mm wafer by about 10 percent.
CMP or chemical mechanical planarization as it is called is the underlying process for polishing lenses, plastic covers and even removing flaws in paint. It is also part of the slurry distribution systems used in hard drive manufacture.
Lemon Pledge has no abrasive components, so it is probably a temporary solution caused by a waxy base filling the scratches. Brasso is a bit more dangerous because it dissolves the plastic slightly but the solvent quickly evaporates before you can do much damage. Plastic polish actually has micro silica particles (or similar) in it, and it planarizes the surface. The cost of a plastic polish relates directly to its purity and particle distribution curve. Actually success will rely on how good you are at polishing evenly and consistently.
So there you have it. 3 ways to fix a scratch in plastic. Fill it, melt it or polish it.