Are incarcerated felons required to pay Federal income taxes? I don't know, I don't think so. Aren't most prison inmate incomes below the federal poverty level? That would only require them to file unless they actually have an income - say from investments, ect..
Once a felon's sentence is served, their rights are restored - taxation on income (because they then actually have an income) and voting privileges are likewise restored.
Their rights aren't restored after they complete incarceration (sp?) or even after their sentence is completed (fines, probation, etc.). That is what this article is really addressing. The laws in the states (at least in my state) that restrict the right of voting for Felons is a life-time restriction. At least that is how I understand it from a non-lawyer perspective.
I'll add to it that many inmates end up being fined or charged for their time in jail (room and board) so I would add that these debts would also be required to be paid in order to restore the voting rights.
The issue really boils down to the ever expanding set of laws that can result in a felony conviction. It isn't to hard to end up a convicted felon. In my opinion, it is part of the disarming of our citizens.........
If my assumptions are incorrect, then please send me to documents that will set my thinking straight. I have to take off for now, but I look forward to your feedback and everyone else's feedback.