> Bitcoin doesn't have a strong single concept of a 'parent'
I'm using the term "parent" loosely in context here to mean a relationship where an input has constraints applied to an output (or outputs).
>
verify the secure hash chain from its parent to itself so that it knows what the parent looked like
I guess I just don't understand why you would want to do it this way. If you send to an address that has such a reverse-looking script, you could brick funds that came from the wrong parent. With the reverse mechanism, the transaction creating the child, you can prevent this from happening by defining the transaction creating such a child as invalid unless the child matches the covenant in the parent.
> "you can only point back so far" leads to transactions becoming invalid, which is something we've always strictly avoided because it can result in huge problems during reorgs
I'm surprised to hear you say that. I have tried to learn why valid transactions that can become invalid is seen as such a problem. I've been unsuccessful in finding much information about this. I tried to document the full extent of my understanding in
my proposal here where I actually have a quote from you where you said you don't think this is a valid concern. Did something change your mind? Or did I misinterpret you? What am I missing from that section I linked to?