PNG can capture build time with the tIME chunk or custom keywords. These timestamps are currently removed by strip-nondeterminism, so are not visible to diffoscope anymore. Yet fixing the root cause would be nice.
Packages which intentionally capture the username or hostname into a custom format, but aren't obviously using any tool or system which has this as a core issue. Interesting because they could be fixed by fixing these things at build time.
Our notes about issues affecting packages are stored in notes.git and are targeted at packages in Debian in 'unstable/amd64' (unless they say otherwise).