strange behaviour of .after() in 2.0b1

the following works fine with jQ1.9 but not in 2.0b1:

$('#comments').after(responseText);

the setup:

<tr id='comments'>

<td> </td>

</tr>

<tr>

<td>end of comments</td>

</tr>

in jQ 1.9 it is inserted correctly:

<tr id='comments'>

<td> </td>

</tr>

<tr>

........

</tr>

<tr>

<td>end of comments</td>

</tr>

in jQ 2.0b1 it looks like that

<tr id='comments'>

<td> </td>

</tr>

<tbody>

<tr>

........

</tr>

</tbody>

<tr>

<td>end of comments</td>

</tr>

have no idea where the tbody is generated. it breaks my layout. in 1.9 it's not there...