Q. Re – question 1660 (In regards to speaking during Hallel at the Pesach seder) – Why do you say that our tradition is not to say a Brocho? Every Haggodo ends Hallel either with the Brocho said normally at the conclusion of Hallel, or with the Brocho of Yishtabach (according to our Aschkenazic tradition).
Secondly, how can the principle of “ein masichin al kos shel brocho” apply here? Maggid is said also with the 2nd Kos, and there we talk and discuss plenty.
Chag Kosher V’Somayach,

A. Unlike the Hallel recited during tefilah, we do not recite a brocho at the beginning of the Hallel said during the Hagada reading. (See O.H. 422: 4, in respect to talk being a hefsek during Hallel in tefila).
In regards to your second question, Horav Shlomo Miller Shlit’a explained that during the maggid section of the Hagada the mitzva we are performing is telling the story of yetzias Mitzraim and explaining it, is part of the mitzva. Not so during the Hallel section, when we are engaged in praising Hashem. This being similar to what we say (Shabbos 10a)” Z’man Torah lechud Z’man Tefila lechud.” Tefila and praise to Hashem, stand separate and are different from Torah learning.

Rabbi A. Bartfeld as revised by Horav Shlomo Miller Shlit’a