Not sure if there are any hacks, it's a relatively simple concept.
A better way for threads since it is in a table is to actually use Javascript.
If you go to the showthread_threadbit_level1_post and showthread_threadbit_level2_post you can add some inline JS code to the <tr>'s. Make sure you strip the classes from the <td>'s so that the <tr> takes precedence.
Make the <tr>
Code:
<tr onmouseover="this.className='somestyle'" onmouseout="this.className='originalstyle'" class="originalstyle">
Note: this will prevent the colors of the backgrounds from changing when using the inline mod. You can prevent that by using javascript on the <td>'s instead but it wouldn't be such a generic code.
Make sure you define the classes in the css.