If your bankruptcy was discharged, then you are free of your obligation to repay the subject debt. The creditor could theoretically report your account as paid in full, if you were to actually do so, but it has no obligation to make any further reports, because the debt is discharged and uncollectible.
The reality of credit reporting is that the smallest defect in performance (e.g., one late payment) will have a dramatic effect on your credit score (typically a 100+ point drop). A bankruptcy will have an even more dramatic effect. The only actions that will restore your credit score to normal is the expiration of the reporting period, which for an individual debt is seven years from the date of the first late payment, and/or 10 years from the date of filing of the bankruptcy case (15 U.S.C. Section 1681c(a)(1)-(2)).
Consequently, I see no advantage, whatsoever, in voluntarily paying off the debt, because the credit scoring algorithms do not take such voluntary (albeit laudable) conduct into consideration.
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