It can be a bit difficult to see where all this washes out, so I’m going to give my understanding of the conversation and maybe someone can confirm or correct:
My understanding of how the function was developing is that Immutable Data is there perpetually, as is, at the address equal to the hash of it’s content. Access to that is only possible by someone holding, or having access to the data map for that IM. No change here.
To put up a web page or site, Mutable Data could be used to point to IM and other MD, basically exposing the data map to each. An owner of the MD (whether solo or shared ownership) could change the “site map” MD and add, delete any or all the referenced links, even deleting the whole site by zeroing the MD. Deleting a link to other data would hide it again as far as that link is concerned. If someone copied the data or retained the data map, they would still have access to it and could pass it on to someone else or make it public elsewhere, but that is a situation that is never going to change, I think. This allows someone a high degree of control over who views their data and how long it is exposed to access. If they accidentally publish a data map to content meant to be private, they could change the MD site reference and minimize the damage, much like is done on twitter, etc., at least from the users perspective.
Appendable Data enters the situation of making even that immutable, but appending changes. If one wants to hide references to other IM or AD, the correction would be made by adding the change so that the desired result would be exposed by default. Though it might be less than trivial to explore and reveal the history, it’s there and accessible via the original MD forever.
Am I wrong in understanding that all that has then been publicly revealed at any time is then publicly accessible forever via that AD? I mean, that’s the point of perpetual data, and it still is true to a large degree with MD. It’s just more complete and history of it all is discoverable right there with AD. It doesn’t mean that a mistaken post that’s changed will be more obvious with AD, just more discoverable after the fact, even if no one saw it in the first place.
Aside from the technical execution advantages/disadvantages, does that pretty well frame the key points at issue?