[Cronos]

your question was -- Annalex said "a Catholic is instructed to examine his conscience before presenting himself for Holy communion", to which you said "Interesting. So here the Roman Catholic is to trust his conscience, but the Protestant who believes in Jesus Christ is not to trust in or rely on his conscience. " ---> apples and oranges: Annalex says about examining your concience prior to Holy communion and you ask a question about some trusting their conscience to follow the teachings of Machen like the OPC does and to make Machen some kind of demi-god if not God.

Why do they do that?

[maryz]

Psst! She apparently doesn't know what an "examination of conscience" is! One may rely on an "informed conscience" (technical term here!), though not on an "uninformed" or badly formed conscience; examination of conscience is a recommended constant practice to keep one's conscience from getting lazy, going astray, becoming self-indulgent, etc.

Everyone certainly must act in accordance with his conscience, but we also have to take care that our consciences are in good working order -- doesn't happen automatically!