"The key idea in Habrmas’s theory of communicative action is that speech acts cannot be planned or executed with entirely strategic intent."
(Communicative Action and Rational Choice, p. 4)
" . . . recent game-theoretic research lends considerable support to Habermas's claim that speech acts cannot be instrumentally rational." (ibid. p. 5).
I don't think Habermas has ever claimed that "speech acts" cannot be used strategically! In fact the possibility that speech acts can be used strategically is the very basis of Habermas' distinction between communicative action and strategic actions! Thus we can define strategic action as a type of action coordination where the primary mode of action coordination is non linguistic and where “the speech acts for their parts are subordinated to the exertion of influence or actors who affect one another purposively that the specifically linguistic binding and bonding energies (Bunungsenergien) remain unused.” (OPC: 220-221). In communicative action “the illocutionary forces of speech acts assume an action coordinating role” while in strategic action the illocutionary force of speech acts is not the primary medium of action coordination. The speech acts are subordinated to the intentions and plans of actors and are used only instrumentally or strategically.