I was once shadow banned because I had submitted a link incorrectly (switched the link & the title which apparently many bots do). I emailed dang and he sorted it out in a matter of minutes.

In my experience the mods are super responsive and more than willing to look into things & hear you out. If this person cares enough to reach out about it they should have the opportunity. And if they’ve been shadow banned for a good reason I imagine they would be told as much.