Your answer to OLD REGGIE illustrates the circular reasoning that I've been talking about. Of course they didn't say Honorius' letter was infallible, for the simple reason that they didn't believe in papal infallibility! The concept was unknown to them, as evidenced by several hundred years of church history after Honorius. You have post 19th century glasses on which render you apparently unable to see the historical facts that Councils and Popes subsequent to Honorius, as Philip Schaff puts it, "... believed that a Pope may err ex cathedra in a question of faith and that one of them at least had so erred in fact."
Your interpretation of the historical facts is anachronistic. Your defense amounts to, as I've said, a "he didn't really mean it infallibly" excuse.
Cordially,
You are switching topics. OLD REGGIE tried to say that the council passage implied that Honorius' letter should be considered infallible from the Catholic perspective. Are you supporting OLD REGGIE's contention?
Bingo!