Burning Kapton is . . . better? In most circumstances?
About as healthy as any good kitchen fire. It's better than PVC, which produces large quantities of hydrochloric acid when burned, but Kapton is also more likely to cause a fire due to poor abrasion resistance. Teflon is nearly as heat resistant as Kapton and handles abrasion much better. Its decomposition products will kill birds and make people sick, but if substantial amounts of Teflon insulation are being thermally decomposed, it's probably unhealthy to stick around anyway. (Note: don't leave Teflon-coated cookware empty on a hot stove.)
Silicone is probably the best thing to have in a fire, just don't breathe the silica dust that results.