... to a mirror finish make it less likely to collect carbon and subsequently reduce detonation?????

 

yes

 

wouldn't it be even more important to get the recesses as opposed to the rest of the face?

 

since none of the faces are supposed to make contact with the housing, all parts would be prone to buildup. Polishing the recessed area would help economy by giving better flame propogation, but since the design basically sucks anyways, it would be more useful to prevent buildup in the first place.

 

to what degree and is this somthing that is done regular or just to squeeze alittle ... is it a noticable difference