No, that's the moderator's responsibility to explain why they have taken their course of action.
Not in a case like this. There no reason in an online forum like this to give people who violate the rules full information about how they were caught.
If you read the discussions leading up to picking a moderator I don't think you find an agreement on a responsiblity of a moderator to explain everything they do. Nancy has a responsibility to moderate when problems arise but she doesn't have a responsibility to explain everything.
In the past putting to much effort into criticizing moderator actions resulted in this community being undermoderated and we shouldn't repeat that mistake.
I've gotten sufficient evidence from support that voiceofra has been doing retributive downvoting. I've banned them without prior notice because I'm not giving them more chances to downvote.
I'm thinking of something like not letting anyone give more than 5 downvotes/week for content which is more than a month old. The numbers and the time period are tentative-- this isn't my ideal rule. This is probably technically possible. However, my impression is that highly specific rules like that are an invitation to gaming the rules.
I would rather just make spiteful down-voting impossible (or maybe make it expensive) rather than trying to find out who's doing it. Admittedly, putting up barriers to downvoting for past comments doesn't solve the problem of people who down-vote everything, but at least people who downvote current material are easier to notice.
Any thoughts about technical solutions to excessive down-voting of past material?