Nope, nesting works! The required ending tag on table means any nested table will open a new context and then any <tr> or <td> will now scope to that table and will until the second tables closing </table>.
<table>
<tr>
<td>
<table>
<tr>
<td> table-cell-inside-table
</table>
</table>
Only a madman would nest tables!!
/me crying in 2000's web design.