Unfortunately, there is no way to do so at the moment, unless you get a job working for Amazon. If you don't mind, please send Amazon feedback asking for this feature. Maybe if enough of us do so, they'll finally get around to it someday.
Oh I would love to have this feature . Would be nice to know before I dont do a hit for a requester I am not familar with or just do a few, or worse yet do a bunch for one who likes to reject just not to pay. And I have heard there are some who you will get rejections from either becasue they dont know how to use the system or the system is not set up for them well and they have to work the kinks out.
I think it might be cool to add sort of a review system for requesters on this forum if Amazon does not choose to implement it on their site.