This is the language of the law court. To write against someone is to make a formal legal charge, accusation, against them, precisely stated and with tight legal argument.
In particular Job complains that he is reminded of the sins of the past as if these had not been forgiven and were still ready to bring him down to hell. It is a terrible thing to have lived a dissolute youth, for as Barnes says, long years may pass and no recompense seems to come on a man; he may enter periods of prosperity and happiness, but God has not forgotten and has power to recall all the offences of an early life. The unbeliever has no defence against this. The believer must remind himself that God has forgiven him and give thanks for God’s grace, but the shame and horror of what he has done in the past may affect him deeply and he may struggle to obtain peace of mind about these things, when faith becomes reduced. Barnes says, ‘The sinner walks over a volcano. It may now be calm and still. Its base may be crowned with verdure, its sides with orchards and vineyards; and far up its heights the tall tree may wave, and on its summit the snow may lie undisturbed. But at any moment that mountain may heave, and the burning torrent spread desolation everywhere.