Alright, the #pages functionality on #CalcKey... needs work. (And maybe #MissKey too - haven't seen their version yet.)
Really - it boils down to the Markdown subset. Pages uses regular post-level MFM - which means no headings, no lists, and no ![]() embedded images.
Images and headings have to be added as blocks - and they don't even work right. Narrow images scale up to the entire width of the page, and headings, or "sections" have only one block.
There is no bulleted list support either - you have to do that manually by using unicode characters.
Also - blocks can't be moved, only added or deleted. There is a move button but it doesn't seem to work - or maybe its a menu button that doesn't work. Either way - doesn't work.
Not only does this make the editing experience a bit painful - making it so that you have to leave the text and add blocks separately - it also means that you can't just write something in an external markdown editor and simply copy into a page - you have to manually split up the text into blocks so you can insert images or sections in-between.
Also - it's very undocumented. I don't know what the variables or the scripting do - you have to figure those out on your own.
That's not to say that pages suck entirely, the interactivity that you can add with forms, variables and scripting is frankly excellent. But if you can't add the content you want, the way you want it - that interactivity is just useless.