Currently there is no way to specify more than one user as assignee or reporter when creating a filter. Also, there is no way to allow users to create groups to use 'filter groups' w/o giving them administrator privileges.
This has nothing to do with allowing an issue to be assigned to more than 1 developer (ref 1802).
The use case here is a large development group with several team leaders managing several projects. Often developers working on the same component report to different managers - so managers cannot use a simple group to get a list of all the issues their developers are working on.
In this case the only way to resolve is to either 1) create a list of group names based on the manager name which contain developers who are currently reporting to them or 2) allow managers to create filters specifying multiple users in the assigned to and reported by filter fields.
Option #2 is superior as it reduces the work load of the supporting IT staff and reduces frustration of the SW managers who otherwise have to wait for IT to fullfill their requests and then wait for the system to be reindexed in order to use the filter.
As this is important to us I've tried to link it to every issue somewhat related.