@Volker_E seems fixed as the result of reverting T150377.

screenshot from production (macOS/Chrome)

Darn, I already had such a nice solution for this in mind. :)

For completion, in case we're introducing outside again:

.mw-references-wrap.mw-references-columns:first-child {
    margin-right: -1em;
}

.reflist ol.references {
    padding-right: 1em;
}