Insert a comma or other separator between Tags and Categories

To insert a comma or other separator between Tags or Categories in the Template (%post_tag% or %category%) use the :after CSS pseudo class and add this selector to your Customizer.

CSS to add a comma between Tags:

.cat-post-tax-post_tag a:not(:last-child):after
{
    content:",";
}

CSS to add a comma between Categories:

.cat-post-tax-category a:not(:last-child):after
{
    content:",";
}