Since Pesach is on the horizon I've gotten started learning some of the halachos of Pesach. In the leining for Pesach (from Bamidbar 28:23), we have a command:
Make an eilleh.
Since the verb תַּעֲשׂוּ is second-person plural, it is obviously referring to the congregation listening to the keriat haTorah. Naturally, in most good shuls, the congregation fulfills this mitzvah by singing the following word, כָּאֵלֶּה (kaeilleh), along with the ba'al keriah. I imagine that this is a very important mitzvah since we read about it all eight days of Pesach.
Yet I have seen that some people appear to look down on the practice of observing this mitzvah deoraita. Interestingly, the person in the thread linked above also appears to disapprove of the rabbinic institutions of singing along with "simcha liartzecha visason li'eyrecha", "bichag hamatzos bichag hasvauous...", and even "tov umaitiv hedoresh lanu" from the Yom Tov shmoneh esrei. *
I would have thought that the person who posted that thread was simply an am haaretz gamur midoraysa except for the fact that even here on Mi Yodeya some apparently frum Jews look down on people who want to fulfill this important mitzvah. Someone even published a book referring to people who do this as nudniks. How can people speak with such disdain about fulfilling what is obviously an important mitzvah
* Though for some reason he doesn't mention singing along with "Avraham yage-e-el" during Shabbos mincha. I thought this was part of the same rabbinic institution. Am I wrong about this?