Do you consider it possible for a user who was previously banned for violating community rules for a long period of time to participate in the moderator elections?
In particular, the user was banned for insulting on nationality.
The user is not currently blocked.
The user used to think this behavior was allowed for himself/herself, but now he/she might be a moderator.
If a user has been suspended on any site in the entire SE network, then they are currently not eligible to run in an election anywhere in the network until at least 1 year after the suspension is over: Let's disallow moderator nominations from people who've been suspended in the past year.
After that 1-year period is over, PolyGeo is correct that past misdeeds are forgiven. However, if you are concerned about that user becoming a moderator because you think they are likely to do the same suspension-worthy thing again, then you might be happy to know that they would lose their diamond if they make insults related to peoples' nationality again.
My understanding is that when a user completes a suspension any past misdeed or ill-advised behavior is forgotten. It does not prevent such a user from being nominated for the position of moderator. Only if that suspension concluded within the last 12 months would they even be shown the banner advising that their candidacy appeared problematic - see Make rules about candidate eligibility due to suspension more apparent.
If elected as moderator, then every action they take is visible to the other moderators, and most of them are visible to the community too. Consequently, I have confidence that they would not be able to act in contravention of the Code of Conduct while in that role, and I would not anticipate them trying to.
