As I am rather new to the use of Mercurial it took me a bit of time to find an equivalent to Git's

# git config --global user.name .....
# git config --global user.email .....

earlier today. The answer is editing ~/.hgrc like

[ui]
username = First Last <mail@example.org>

as I learned here eventually. I should have learned it from the Command equivalence table, though. So I have added an entry myself now to speed up whoever runs into that problem next.