Natbib agsm - remove comma from subsequent authors in bibliography

My dissertation requires a very specific format of Harvard-style referencing, with a comma only after the first author in the bibliography, like so:

Simmons JG, Badcock PB Whittle SL Byrne ML Mundy L Patton GC Olsson CA and Allen NB (2016). The lifetime experience...

I am using natbib and an version of agsm edited to remove title quotes, comma after year and periods between author initials (also required), producing this:

\begin{filecontents*}{\example.bib}
title={The lifetime experience of traumatic events is associated with hair cortisol concentrations in community-based children},
author={Simmons, Julian G and Badcock, Paul B and Whittle, Sarah L and Byrne, Michelle L and Mundy, Lisa and Patton, George C and Olsson, Craig A and Allen, Nicholas B},
journal={Psychoneuroendocrinology},
volume={63},
pages={276--281},
year={2016},
publisher={Elsevier}
}
\end{filecontents*}

\documentclass{article}
\usepackage{natbib}
\bibliographystyle{agsm-mod} %issue is the same with unmodified agsm
\let\oldthebibliography\thebibliography
\renewcommand\thebibliography{\let\bf\relax\oldthebibliography}

\begin{document}

\nocite{*}
\bibliography{example}

\end{document}


What do I need to change to get the format I need?

• It never ceases to amaze me how universities and other entities manage to waste time and sow confusion by coming up with ever more eccentric formatting requirements for bibliographic entries.
– Mico
May 7 '20 at 12:18
• BTW, what's the formatting requirement for entries with exactly two authors? Should they be separated a comma or an "and" (or, possibly, both a command and an "and")?
– Mico
May 7 '20 at 12:19
• Entries with exactly two authors are to be separated by "and" May 7 '20 at 12:48
• What makes this really challenging to program is the requirement to insert a comma after the first author while omitting all further commas. If all commas could be omitted, the task would be quite straightforward, actually.
– Mico
May 7 '20 at 13:14

Please note: The following is only a partial solution, in that it removes all commas after and up to the penultimate author in a list of authors. Thus, it won't create

Simmons JG, Badcock PB Whittle SL Byrne ML Mundy L Patton GC Olsson CA and Allen NB (2016). The lifetime experience...

but only

Simmons JG Badcock PB Whittle SL Byrne ML Mundy L Patton GC Olsson CA and Allen NB (2016). The lifetime experience...

I will cross my fingers that is better than nothing at all. If this way of proceeding is acceptable to you, I suggest you create the formatted bibliography (stored in the file \jobname.bbl) and hand-edit it to re-insert the commas after the first author if an entry has three or more authors.

A separate comment: The requirement to provide a comma after the very first author's full name not after authors 2, 3, ... , n-1 (assuming an entry has n>2 authors) makes absolutely no sense to me. I believe one should either show no commas at all or show commas after every author up to the penultimate author. (The comma after the penultimate author is called the "Oxford comma". I'm aware that viewpoints tend to diverge wildly on whether the Oxfor comma is called for or not.)

I suggest you proceed as follows:

• Open the file agsm-mod.bst in a text editor.

• Find the function called format.names.

• In this function, find the following line:

        { ", " * t * }


Change it to

        { " " * t * }


i.e., remove the comma but leave the space.

• Save the file agsm.bst and perform a full recompile cycle -- LaTeX, BibTeX, and LaTeX twice more.