What is the formal code review process of the standard client?
According to the bitcoin.it wiki, as Stephen Gornick linked to in a comment, this should be the code review process:


  Pull requests are discussed on the forums and if there is consensus they're safe, tested, useful, well written, match coding style, etc. then they're merged into the 'master' branch.


Assuming the bitcointalk.org forums, I can't really find any pull request discussion. On Github it seems pull requests do get discussed though, for example: Bloom filter pull request.