Manifold's policy right now is to allow creators to N/A a market for any reason, even if it's blatantly incorrect or fraudulent.
To be more precise, there is no policy except some vague suggestions in the community guidelines. Every time one of these situations occur, the mods have the exact same argument over what should happen, and arrive at the exact same conclusion of "no clear decision has been made, just do whatever". Usually "whatever" ends up being "allow the creator to resolve N/A if they want to", though it's inconsistent.
Here are all of the relevant excerpts from the community guidelines:
Markets designed to defraud users [will be] retroactively N/A’d, or N/A’d if the creator is banned for defrauding users on other markets.
Market creators have the right to N/A their own personal goal markets.
Manifold or moderators may resolve a market on your behalf if unambiguous resolution criteria are fulfilled. This could include un-resolving a blatantly incorrect resolution made by the creator.
Manifold reserves the right to re-resolve any market if we believe they were resolved fraudulently, including markets created prior to this policy coming into effect.
So the official policy is "we're allowed to fix improper resolutions, but we make no guarantees to do so, and also creators are allowed to misresolve personal goal markets and markets that Manifold deems 'fraudulent'".
This is obviously terrible, as it steals arbitrarily high amounts of opportunity cost and counterfactual mana from traders, allowing creators to cap their losses in their own markets at M$0. It's like saying that the game "let's bet $5 on this coin flip, except if it lands in a way I don't like I get to nullify the bet retroactively" is a fair game. As far as I'm aware no justification has ever been provided for this policy, but Manifold and the mods keep doing it anyway. (Wasting their own time in the process with all the identical arguments over this.)
This market resolves based on whether Manifold implements and consistently enforces a new policy that clearly disallows improper N/A resolutions.
Related questions
From the FAQ:
Manifold puts trust in its users to resolve their own markets in a timely and accurate manner. We generally will not intervene and resolve a market ourselves outside of exceptional circumstances.
Markets creators who are known to be reputable will earn followers, positive reviews, and more activity on their questions.
It seems to me Manifold is hoping that as a trader you just won't waste your time with markets that are likely to resolve NA for unjustified reasons. Even if they completely removed NA as a possible resolution, as a trader you'd still need to be on the lookout for bad markets. Markets that resolve in 50 years, markets with unclear resolution criteria, markets with a creator that will have probably forgotten this site exists by the time resolution day comes, etc.
As somebody expecting to lose a lot of mana in a personal goal market, the idea that Manifold permits users to NA personal goal markets is very funny to me. I won't do it, of course, and I agree with you that it shouldn't be allowed.
NA is often not a resolution. It's "canceling the market". There are many markets that I haven't created; creating them and then canceling them if they are low-value or I won't have time to judge them would be a good way to measure demand for such markets. I have in fact added a clause to that effect for markets requiring a lot of effort.(minimum # of traders or volume)
Your complaint about opportunity costs is better solved with a portfolio margin system and better use of leverage.
In general, it's stupid for people to be betting on markets expiring in 2031 or later for the simple reason that Manifold's churn rate is high enough that it would be unreasonable to expect anybody to stick around that long to judge their markets. Canceling them when they realize this is honest. Moderators could also resolve them, but moderators are also leaning more towards NA'ing such markets to reduce their workload.
Any of my markets expiring later than 2024 are very likely to be NA'd if they aren't important enough to be delegated. Which is why most of them expire before then...