The obsolete/unstable checkboxes seem to be handled by cell, should be by column

[afmenez]

It seems the results are added/removed by cell, which confuses older browsers (see #1127). And is also slow on all browsers, as it triggers a lot of unnecessary reflows.

How about adding/removing entire columns? I believe the "col" element can be used for this:

<table>
  <col />
  <col style="visibility:collapse"/>
  <tr><th>visible</th><th>hidden</th></tr>
  <tr><td>visible</td><td>hidden</td></tr>
</table>

This would also help with #1146, since the table width would be known from the start.