Jeff Stedfast's email about gmime-filter-headers.c possibly being unnecessary with GMime 2.6 (quoted in id:87bo56viyo.fsf@nikula.org) sent me on a wild goose chase that led to this patch series. It turned out that we *did* need gmime-filter-headers for what we were doing in the reply text format, but what we were doing made no sense. Patches 1 through 4 are simply the documentation and tests that I left in my wake and are harmless to push. Patch 6 is my conclusion that how we were handling header encoding in the text reply format made no sense. Patch 5 is a step toward patch 6, but makes sense on its own even if we decide against patch 6.