This discussion really belongs in Site Talk if anything is to come out of it.
My thoughts.
1.) Requiring header information probably isn't ever going to happen here. Anything that can't be automatically enforced won't be added. We're eliminating staff bottleneck not giving new responsibilities and creating more. I also don't read many of the languages patches are submitted in here, so I can't even check the readme even if the information is there and I wanted to.
2.) This information belongs in the Patch Comments section. A good handful of entries already have header or no header information present there if the information was readily available.
3.) As Gideon pointed out, the information may not be known. Also remember, patches are submitted here by people other than the original author.