I was able to fix this. I use Buddypress over Wordpress with QA intergation and this is what I did to fix the issue:
1. In qa-question-followers-widgeet.php around line 285 look for this function and the associated changes I have made below. I have replaced table names to point to wp_users where they need to and changed column names to match. What is not available I have removed from the select statement.
'columns' => array('wp_users.id', 'wp_users.user_nicename', 'qa_userpoints.points', 'wp_users.user_email'),
'source' => "wp_users JOIN ^userpoints ON wp_users.id=^userpoints.userid JOIN ^userfavorites ON wp_users.id=^userfavorites.userid WHERE ^userfavorites.entityid=$ AND ^userfavorites.entitytype=$",
'arguments' => array($entityid, QA_ENTITY_QUESTION),
'sortdesc' => 'qa_userpoints.points',
2. Once that is fixed and data is available. Look around line 247. I have changed user[handle] to user[user_nicename] as below
3. Look around line 252 for printing the avatars. This is the change you need to do calling buddypress avatar function.
$themeobject->output('<SPAN CLASS="qa-question-followers-avatar"><A HREF="'.qa_path_html('user/'.$user['user_nicename']).'" CLASS="qa-user-link" TITLE="'.$user[user_nicename].'">'.bp_core_fetch_avatar( array( 'item_id' => $user[id], 'width' => 20, 'height' => 20, ) ).'</a></SPAN>');
4. Make sure you change user[handle] to user[user_nicename] wherever you encounter it in this file. And it is good to work with the setup like mine. Similar changes can be done for tag followers widget as well.