Making a Beracha On A Takana D'Rabanan/Minhag

y good friend the Divrei Chaim has a post discussing the issue of Chazal adding an extra criteria to a mitzvah. This reminded me of something I saw this past Shabbos in a sefer Ohr L'Avraham on Chanuka by Rav Avraham Gurwitz (Rosh Yeshiva of Gateshead). He discusses the question of whether one would make a beracha on Megillas Antiochus in those communities that read it. If I remember correctly this is what he says. The consensus was not to make a beracha. The question is why would this be any different then making a beracha on Hallel Rosh Chodesh or Haftorah on a Ta'anis? He answers that it depends on how we view the takana? If it is based on a previous din then it would require a beracha. Therefore, Hallel on Rosh Chodesh is based on Hallel on Yom Tov and the Haftorah during the week is based on the Haftorah on Shabbos. Therefore, we make a beracha. However, reading Megillas Antiochus is a new minhag and not based on anything and therefore does not require a beracha.

Although he doesn't say it in so many words, I believe he is saying that it is a question of extension vs creation. If the minhag is an extension of the old din we can make a beracha but if it is a new din by itself (creation) we don't make a beracha.

NOTE: I am writing from memory and I could be missing some nuances. If it doesn't make sense it is my fault.