A year ago, I was banned from r/politics after accruing about 450k karma from that sub alone.
I had a temporary ban of 3 days for some choice words I shared with a Trumpist.
A couple of days after the ban ended, I got perma-banned for violating the previous ban, which I didn't think I did. When I asked the mod team, they responded that reddit AI or a bot had detected it. They gave me a link that said the bot does detections but is not 100% perfect. I asked for evidence. They refused because they didn't want to reveal how the bot worked. They told me I could contact reddit admin instead. Reddit admin responded that I could contact the mod team for that sub... That was some Kafka-esque shit.
In any event, the perma-ban came with the threat that I would face a sitewide ban if I tried to evade the ban. The mods can't do that, but reddit admin can.
I assume they are looking for other accounts with the same IP address to detect ban evasions.