Did he? I was under the impression he wasn't approved to write C at Google when Go was initially being developed.
http://www.theregister.co.uk/2010/04/21/ken_thompson_take_ou...
http://www.theregister.co.uk/2010/04/21/ken_thompson_take_ou...
There is a "readability" process for C++, which is the thing he says he never got. Not much code is written in plain C -- the Go compilers would be an exception.
If I recall correctly, the book Coders at Work also talks a bit how the some of the Go/Plan 9 guys sat near to Bjarne while he was developing C++ at Bell Labs. They are not really fans :)
It's not that strict.
Google has a big source repository which holds essentially all applications which run on Google's production machines. (They share a lot of library code.) In this repository, code written in any of several languages must have been written or approved by someone who has "readability" in that language. There's no C readability, but C++ readability applies to files ending in .cc or .h. (Not sure about .c.) There's no shortage of people around with C++ readability, so Ken wouldn't have had a hard time getting anything approved. He also could have easily gotten readability if he wanted it.
This process wouldn't necessarily apply at all to separate git/Mercurial repositories used by open source things like Go.
Use your local git(1) for better history browser.