This quote is from the Bitcoin Wiki. So if the use of other implementations is discouraged, where is the consensus? “There are a few alternate full node implementations, but they are not recommended for serious use because it is currently difficult to determine whether they implement the consensus rules with 100% accuracy. Even very slight inaccuracies could cause serious problems for the users of these alternate clients. Example of implementations libbitcoin, btcd, a list of other Full Nodes.”