You could lap it Im sure. Its not a coating, its a solid piece of stainless. Have done this with heatsink bases before. The main thing is to use super fine wet/dry sandpaper, and stick it down on a hard smooth surface (like a piece of glass).
Replace the word "heatsink" in this article with "Tamper" and you will have a good guide: http://www.overclockers.com.au/wiki/How_To:_Lap_a_Heatsink
Edit: found the posts you were referring to: http://coffeesnobs.com.au/YaBB.pl?num=1259967195/19
Id personally take an "if it aint broke dont fix it" approach, and not bother unless the dents are bigger than a grind of coffee (relatively large compared to say, a scratch.