This is a really obvious feature that needs to be added to FB.
Usually when you write a bug, you want to include a list of people who all have a stake in the bug, usually this is because these people are affected by it, affected by the fix, or need to provide information or approvals for the fix.
This style of bug is not to jump sequentially from Person A to B to C to D, instead it is Person A,B,C and D all providing input and receiving updates for the bug as all parties have some stake in various aspects of the issue.