SERVER-17856 added support for users on mongod running currentOp and killOp against operations they themselves had started.
From that ticket:

Both the inprog (currentOp) and killop (killOp) roles are granted at the cluster resource level, which makes them an all-or-none condition (I believe).

Use case:

Give developers access to a database with restricted access (basically read-only, non-administrative authority). However because they are given the ability to execute queries, it would be nice if they had the ability to kill any process that were executed by them. Some tools, such as Aqua Data Studio, utilize the killOp command to terminate any queries executed from their query window, however this functionality only works for individuals with administrative roles.
One solution would be to permit killOp command to be permissioned to allow a user to kill his own processes but no other.

Perhaps even just a single new role (userKillOp?) could suffice.

Though harder to achieve, this functionality should work on mongos as well.