I've made a market based on how manifold will change, which I think is more objective than interpreting an article by 538.

This market could do with an upgrade @ManifoldPolitics

It's being cited e.g.

But tiny bets swing the % a lot.

Selling at slight profit here in order to invest in https://manifold.markets/jacksonpolack/if-kamala-harris-debates-donald-tru which will N/A if the debate doesn't happen.

If Kamala Harris debates Donald Trump before the 2024 election, will Harris win? (from polls)

65% chance. Resolves based on the first such debate, resolves N/A if no such debate happens. Will resolve based on polling conducted about the debate. In the past, 538 has covered presidential debates by sponsoring polling of debate viewers and asking them who won. If they do this again for the first such debate in the 2024 election, this market resolves based on that. If there are several questions polled about the candidates' debate performance, this question resolves based on the closest thing to the question "Overall, who do you think won the debate?" If 538 does not sponsor their own polling but does have a definitive post-debate article covering other polling, perhaps averaging different polls of debate viewers, this market will resolve based on that coverage. If 538 does not do that, another source of similar polling will be used. If none is available, this resolves N/A. Criteria will be updated as we learn about if and how the debate will happen.

I'm confused. The question says "IF" they debate, so why is there an option that they don't debate? It should just refund if the debate does not happen and not have that third option. There are separate questions on probability of debate happening at all

I've answered this at length in the VP debate market - you can see the comments here:
/shankypanky/if-kamala-harris-and-jd-vance-debat

It was a deliberate choice to add a third option to avoid NA here. I understand there are people who don't like this format/framing and would rather not bet - and you're right that there are other markets (or opportunities for markets) on the topic! Here's a binary from @jacksonpolack that you may prefer:
/jacksonpolack/if-kamala-harris-debates-donald-tru

Hate polls? Then bet on vibes!

NewsWire tweeted:

and Trump has stated he would debate the Dem nom but it should be on Fox News because outlets such as ABC are "biased":

https://truthsocial.com/@realDonaldTrump/posts/112826639924748087