I messaged the admins and one told me I was involved in a vote brigade over a week ago. I denied it (because it wasn't true to my knowledge and my use of reddit has been sporadic in the past weeks for obvious reasons) and asked for proof, or to at least tell me what sub it was in so I could know if it's something I downvoted by chance and to explain myself. After much arguing and denial on their part to show any proof or anything they stopped replying to me and the ban was lifted. I think it was because my account had been subbed to several now banned subs. That's the only thing I can think of. If they have access to what you up and down vote I'm sure they have easy access to who's subbed to certain subs.