what happens to formulas when rows or columns are inserted, deleted or moved.
Inserting, deleting or moving rows and columns changes the position of every cell after the edit. Formulas that pointed at those cells have to be rewritten so they still point at the same data: insert a row above row 3 and =B3 must become =B4.
Deleting the referenced cell is different. There is no longer anything to point at, so the reference becomes #REF! and the formula must be repointed by hand. Ranges shrink rather than break when only part of them is deleted.
Most spreadsheets perform this rewriting invisibly. deepcalc journals it: the structural edit and each formula rewrite land together as recorded operations, so a diff shows precisely which edit changed which formula, and blame can answer who moved the data.