`***strong** and italic*` compounded expression does not end

[KSR-Yasuda]

**strong** and *italic* compounded expression, such as below would not close.

foobar
***foobar**foobar*
foobar

foobar
foobarfoobar
foobar

In the syntax, it is handled as mkdBoldItalic, but it must end with *** or ___.
So, opened mkdBoldItalic is not closed by the separated ** and *.

Is this unavoidable in Vim code, and we have to give up the ***strong-italic*** markup?