No hack is required, just use the already existing User Rank Manager to assign people in certain groups a rank and then display the rank in your postbit.
For example, I have a User Rank named "Super Moderator" that requires 0 posts, is always displayed, and is stacked. The trick is to then select the "Super Moderators" usergroup for the new rank. The result will give you something like
this. In the first post notice the display for the thread poster... "Creative Writer" is his personal user title that he entered while both "Community Member" & "Super Moderator" are ranks that he was automatically assigned.
No hacks, no edits required.