spacing in scripts

There are three proposals about how horizontal spacing in scripts should be
handled in MathML core: follow TeX (no spacing), follow MathML (same
spacing as on the baseline, shrunk because of a smaller font), or FireFox's
layout (half of what MathML uses). There are examples in this github bug
comment
<https://github.com/mathml-refresh/mathml/issues/38#issuecomment-552664086>.

We would like to resolve this at next Monday's MathML core meeting (meeting
time/connection info
<https://lists.w3.org/Archives/Public/public-mathml4/2019Jun/0017.html>).
Please add your preferences to the github issue if you have a preference.