I wasn't thinking anything so formal, merely the "norm" that if I post an ad for some shitcoin airdrop I will probably end up getting downzapped.

I think attaching notes to downzaps is probably a bad idea. But I think letting a user see that a post or comment has been downzapped and to what extent could provide useful feedback.

I agree there isn't any norm, but SN, like every community has a culture, and there is a fuzzy edge past which people might do a thing that breaches the norm. They don't necessarily need anyone to tell them this but could benefit from a numeric visual aid to show them they are heading toward the badlands.

Also, I think they should definitely be called zonks.