Is it permissible for a worshiper who frequently experiences flatulence and urethral discharge to repeat the prayer at home before going to pray with the congregation, in anticipation of his ablution being nullified during his prayer?

If you are afflicted with chronic flatulence, you are permitted to miss congregational prayer and perform the obligatory prayer at home. You should not go to the mosque to avoid inconveniencing other worshipers. However, if you are not afflicted with it, then be sure to perform the obligatory prayer in the mosque. If you pray at home and then go to the mosque, you are permitted to repeat the prayer with the intention of it being a supererogatory (nafila) prayer, for the Prophet, peace and blessings be upon him, said: "If you have prayed in your dwellings, and then you come to a mosque where a congregation is gathered, pray with them, for it will be a supererogatory prayer for you both." This does not contradict the hadith, "No prayer should be repeated twice in one day," because its meaning is that prayer is not obligatory twice, and the second prayer becomes a supererogatory one.