I've been recently banned, here are the information for science's sake.
As soon as emuMMC came out, I made a partition based emunand right away (in June I think). I didn't modify anything before that.
I've tried to keep sysNAND as clean as possible and the emuNAND as offline as possible over these months but obviously I screwed up somewhere.
I got banned between monday and thursday (25-28 of May); I don't know for certain since I kept the switch in emuNAND for various days.
Error code's 2124-4508, I suppose my account is fine.
As for CFW I used Kosmos with sigpatches for a bit and then switched to plain atmosphere (still with patches), also I've always booted with hekate. I don't have AutoRCM, I didn't clear any logs and I don't have incognito.
Back in August I put my switch in it's dock, and it was hooked up to ethernet. I was on cfw playing a legit cartridge game but with some .nsp updates installed. I realized after a couple of minutes, plenty enough to get banned although it's weird that they took this much time.
I'm pretty sure that during these days this week I didn't screw up (I have since set up 90DNS on the ethernet profile, as well as disabling autoconnect), however the timing suggests otherwise. Is it possible that nintendo has started scanning the sd card?