Comma after last selector

Given this code

a,
h1
{
  background: lightblue;
}

I would like to rewrite it such that each selector ends with a comma, even the last. This will make it easy to add or reorder selectors. However if I add a comma after the last the style will not be applied. This code seems to work

a,
h1,
_ {
  background: lightblue;
}

but could this cause unforseen issues?