When people edit their Phab profile (via "Manage") and change or remove the Also Known As (AKA), an entirely new identity is indexed.

This should not happen. Code should realize that the actual username is still the same. (Note that this is not about renaming the username which is also possible; I don't expect the code to also cover that by pulling user account IDs or such - different topic.)

e.g. for UID 625b1693d84f510ebdc782bc2bf0806903a3b5e4, https://phabricator.wikimedia.org/people/manage/27796/#11693 shows a change of the AKA. I had to manually merge these two accounts in the DB into one:

Needs changes probably somewhere in https://github.com/chaoss/grimoirelab-perceval/blob/master/perceval/backends/core/phabricator.py