As someone who LOVES the absence of social noise on TSG and considers it "one of my favourite things" (UNLIKE "The Sound of Music"), I still sometimes wish I could silently thank a user for their review.

If it were possible to "thank" someone with no visible indication on the review page that this had been done, the temptation/tendency to 'game the system' by writing for points would still be avoided. If the only result was the user receiving a notification that some unspecified user had thanked them, that would avoid any sense of intrusion, while at the same time letting them know that their contribution was appreciated.