This would be done by marking the question "non-predictive", though it should be noted that this tag's name is a bit of a misnomer.
Context: This market was at 90%, and then a user made dozens of new accounts and bet the 500 signup mana from each on NO.
I think it would be good to get people on record about this before we know the result.
1,000
3.00
Argument for exclusion: These new accounts broke the rules by making a bunch of alts and abusing the free signup mana given by Manifold. It's not very different from someone using an exploit to generate a bunch of free mana, and then betting that mana before the mods can fine them. If this is allowed, users could cheat the system of mana and promote in leagues by generating profit for their main account.
Argument against: It is good for markets to be accurately priced, and there might be less incentive to bet against ill-gained mana if you don't think your profits will count for leagues.