Talk can be used as a verb or a noun, but it is not an adjective and does not have a comparative or superlative form. Talkative is an adjective. More talkative and most talkative are the comparative and superlative forms.
Health is not an adjective and therefore does not have comparative and superlative forms. Healthy, however, is an adjective, with the comparative form of healthier and the superlative form of healthiest.