User blog comment:Martialmaniac/Inferred Nen Type/@comment-4932025-20160620002148/@comment-5780397-20160620105953

I agree with Youpi's ability probably being a combination of Enhancement and a natural ability, but I guess it should be mostly considered unknown (same for Meruem's shapeshifting), possibly with a reference/separate page to list the main possibilities.

So, in Meruem's case, we are considering the card game to be the source?

Don't get me wrong, I am not saying we should guess the Nen type of every abilities. Many will remain "Unknown", but we may make a theory page even in those cases. I don't think we can even speculate about Convert Hands, but The Sun and Moon could be easily explained as a combination of Emission and Transmutation. I would still prefer to leave it unknown and just add a redirect to the inference page/reference, while we could write the type directly in cases like Hisoka's Bungee Gum and Killua's Narukami.