4:15(Protection of honor and chastity for men and women, both, is the cornerstone of a virtuous society. 17:32, 4:24.) If any woman or a group of women spread sexual immorality or lewdness in the society, it is required that the appropriate court takes four honorable and reliable witnesses. If their testimony corroborates with other evidence (12:26), confine them to their houses, since immorality is as contagious as good conduct. This confinement would be for an indefinite period, unless such women seek the Way of God, such as repentance and making amendment, or the singles among them get honorably married.
واللذان ياتيانها منكم فاذوهما فان تابا واصلحا فاعرضوا عنهما ان الله كان توابا رحيما
4:16If the two of you spread such immorality or lewdness in the society, both of them shall be punished (as determined by the appropriate court of law). But if they repent and mend their ways, leave them alone. God is the Acceptor of repentance, Merciful. (This includes homosexuality, male and female.)
If you look at 4:15 it says that women committing lewdness should be punished until they seek forgiveness from Allah and then can be pardoned (after re-education and taught how to act appropriately).
Straight after we have 4:16 which says lewdness should be punished until they repent. To me this is repeating what has just been said so does not make sense. However, if we take the meaning that 4:16 is regarding two men, then the verses make sense; 4:16 is repeating the punishment for men, nor women. You may argue that this is taking the interpretation too far, but when we look at 4:19:-
4:19 O You who have chosen to be graced with belief! It is not lawful for you to force women into marrying or holding on to them in marriage against their will.
We can see that it is addressing men so the addressees of 4:16 can be understood to be men. Hence, the repetition is nonexistent, both verses complement each other.
Parwez Saab has this in his exposition:-
4.15 If any of your women commit indecency, take the evidence of four witnesses from amongst yourselves. If they are proven guilty, restrict their movement by confining them to their houses for life or until Allah opens out a way for them.
4.16 If two men from amongst you are found guilty of something similar, punish them. But if they repent and make amends, then leave them alone. The Divine System makes room for repentance and thereafter the restoration of the means of development.