A very mild in the absence of a reason for this extra paperwork.

If I understand this correctly, that would allow a Nomicer to be in a position where they have to record a Sin (say, a ladder combo), opt not to actually add it to the Sin list (“if that word does not already appear in the Sins list, they may add it to that list at the same time”), and thus be free to treat the word as if it’s not a Sin (eg by using it for a ladder combo again)>

That part is pre-existing. The only new optional part is removing a sin with a prevelance of 0, and the rest is compulsory.

Huh, you’re right. That’s probably not great. Or maybe it is? I don’t know.

This has a scam smell to it, but I can’t quite put my finger on it just yet. Maybe it’s just because, like Kevan, I can’t quite see the utility of it without it being a setup for a scam.

I don’t think this is a scam, but I think it would have been better introduced along with a reason to care about it, so we could judge whether the reason was worth the extra tracking load.