@footnote::before is not discarded

[rhn]

The spec mentions the "footnote rule", but doesn't actually specify how to create it.

I tried to create a 20% wide rule with @footnote::before:

@page
   @footnote::before {
        display: block;
        width: 20%;
        border-top: solid 0.2mm;
    }
}

but the "::before" seems to be stripped and the rule applied to the entire area instead:

Is it reasonable to expect "::before" to apply to the footnote area?