The HotSpot code has inserted the value of HOTSPOT_BUILD_USER into the internal version string since before the JDK was open-sourced. See https://github.com/openjdk/jdk/blob/master/src/hotspot/share/runtime/abstract_vm_version.cpp#L284

It is not clear what value this provides. By default, the value is set to the system username, but it can be set to a static value using --with-build-user.

In trying to compare builds, this is a source of difference if the builds are produced under different usernames and --with-build-user is not set to the same value.

It may also be a source of information leakage from the host system. It is not clear what value it provides to the end user of the build.

I intend to propose removing it altogether, but at least knowing why it needs to be there would be progress from where we are now. We could also consider a middle ground of only setting it for "adhoc" builds, those without set version information, as is the case with the overall version output.