also, do we want to move this to the app, considering that's where all the logic will be and this ADR modifies application specific types?

nice! the only thing left is to add it when splitting shares! simple pimple. well done

Added in 26884d1 . Resolving #842 and merging celestiaorg/celestia-app#637 would make implementing this ADR significantly easier to tackle.

also, do we want to move this to the app, considering that's where all the logic will be and this ADR modifies application specific types?

Agreed. I originally targeted celestia-core because all the relevant issues are in this repo. Resolving this ADR will involve modifying celestia-core types too (e.g. Message struct) but will move to celestia-app because that's where share logic will live long term.