I'm experiencing cutoff labels of when using text placement type 'simple' despite large buffer sizes and trying text-clip:false as suggested by @springmeyer.
Adding text-avoid-edges: true fixes this but does result in fewer labels. I am using tilemill for this, and am not sure how to dump the generated XML - apologies.
(x-posted from https://github.com/mapbox/tilemill/issues/382)
TileMill supports outputting Mapnik XML in the "exports" menu.
I think text-avoid-edges: true is the best fallback to avoid cutting when using placement-type:simple. Then to avoid reducing the # of labels increase your metatile size as big as possible, 16, or 32 if you have tons of memory.
Thanks Dane. Increasing the metatile size worked great.