.comma:not(:first-child) {
    margin-left: -0.3em;
}

/* next 2 rules are for spacing when the first .comma is empty too */
.comma:first-child:empty ~ .comma:not(:empty) {
    margin-left: 0;
}

.comma:first-child:empty ~ .comma:not(:empty) ~ .comma:not(:empty) {
    margin-left: -0.3em;
}

.comma:empty {
    display: none;
}

.comma:not(:first-child):before {
    content: ", ";
    /* padding-left: 0.3em; */
}

.comma:empty + .comma:not(:empty):before {
    content: "";
    /* padding-left: 0; */
}

.comma:not(:empty) ~ .comma:empty + .comma:not(:empty):before {
    content: ", ";
    /* padding-left: 0.3em; */
}