I agree, sharing will (most probably) still work on segment-level [0]. But this means that if I have two different executables each linking an identical version

I agree, sharing will (most probably) still work on segment-level [0]. But this means that if I have two different executables each linking an identical version of, say QT, in its .text segment, those copies will not be shared. [0] In fact, certainly. Program loading works by mmaping the executable with MAP_SHARED flag into the process's address space, and the VFS takes care to keep all mappings coherent. The simplest way of keeping mappings coherent is to actually share the backing storage between all mappings. It's the foundation of CoW.