I agree with those who have noted that regardless of wording, there will always be cases of overconfident disagreeing (as with overconfident agreeing). On the other hand, maybe there could be some tweaks to the current language that would help bridge the gap between “I am confident it is not species X” and “I am confident no one can confirm this as species X given the current evidence.”
For example, the text displayed under the disagreeing ID could be changed from “* [user] disagrees this is Genus species“ to “* [user] disagrees this can be confirmed as Genus species“ (though maybe that tips the language too much in the other direction, and is a bit more wordy).
The biggest issue with the current wording is that it describes ‘leading disagreement’ but is actually ‘branch disagreement’. If I disagree with Vascularplantus wrongus but don’t know what plant it is and just put Plant, then by clicking “No, but it is a member of Kingdom Plantae,” I would think by the wording that I am affirming that it is a Plant, and only disagreeing about the particular species. I would not at all expect that by clicking “it is a member of Kingdom Plantae” I’m actually saying it’s not the vast majority of the species that most people think of as plants (i.e. vascular plants). But that is in fact what happens. Effectively, I think I’m saying “I’m certain this is a plant” when I’m in fact saying “I’m certain this is a non-vascular plant (moss, algae, liverwort, etc.).”
I actually think the proposal at the end of the blog post on Clarifying Ancestor Disagreements is great:
But that was over five years ago…