are possibly started by people who want to prove a theory that mumsnetters will give different advice to a woman having an affair to the advice they would give to a man having an affair?
but that mostly these threads just prove that
a. every circumstance is different.
b. generally mumsnetters do not condone having an affair or keeping an affair secret.
c. the consensus is normally that people should split up with their partner before starting another relationship and lying to someone makes you a bit of a shit whatever sex you are as it doesn't give them any choices.