Not yet apparently.
After a couple months of being in the ACNH scene, I can say that save editing is
somewhat safe —for now—, since Nintendo can't detect any changes you make as of the latest update. But to stay safe in the future, don't make changes that are impossible to replicate in the game. They could be developing an update that makes them easier to identify externally modified data, for all we know.
And yes, while they can identify what items/villagers might be illegal (e.g. star trees, test furniture, wrapped critters, villagers w/ incorrect items), they can't know who exactly hacked them (this itself was
confirmed by Nintendo Japan apparently) because these items can be traded between islands. But still poses a risk, so don't do that.
I've been thinking of some possible flags they might use to correctly identify who's a hacker:
- turnip prices online above ~650; or turnip prices that don't follow a pattern correctly. If you edit turnip prices, use the prophet! (or don't edit them at all?)
- editing your map using NHSE. apparently there's an in-game counter of how many blocks you edit?
- Your achievements not matching your flags count, or setting your achievements to a weird date like 1750 (it is impossible to set a year previous to 2000 on your Nintendo Switch).
- having a villager with a different personality set in NHSE, even though this doesn't work since they're hardcoded, but it's still a variable you can set?
- enabling stuff that doesn't match your other achievements/flags. (example: enabling the nook shopping phone app flag, but you still haven't bought 100 items on the catalog).
Edizon cheats are
NOT safe and if you enabled them online
then you have already been flagged. If you used them, Nintendo has the power to ban you now.
Also, be careful of using CFW online at all. If you re-inject your save using JKSV, it's best that you go back to stock firmware if you want to play online.
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