You could make as many plugins as you need (for each object's group). For example:
com_myextension_djs.plugin.php
com_myextension_artists.plugin.php
And then load plugins as:
JComments::showComments($dj->id, 'com_myextension_djs', $dj->name);
and
JComments::showComments($artist->id, 'com_myextension_artists', $artist->name);
The first code will use first plugin and works with tables related to DJs, and the second one - with artists. This is simple
