The recipient of an artefact also reviews the artefact.
When reviewing an artefact that is produced as part of the development process, the people who need to use the artefact are represented as reviewers of the artefact.
This goes back to common sense. Why do you produce a document or other artefact? It is produced for some purpose; it has some use. The people that are expecting to use it are the best judges of whether or not it is fit for the purpose. Where documents etc. are produced for multiple purposes, they should be judged fit for each of these purposes. This feedback is essential if the artefact is not to have the same sort of problems next time one is produced.
Note that when DevelopingInPairs, if the recipient is one of the pair, then he will in effect be reviewing and giving feedback as he goes. One cannot arrange work so that is always the case, but if one arranges things so it is occasionally the case, it can be very beneficial.