Strongly disagree. They are every bit a part of the USC. That's why they're called amendments, and the USC has a formal process for changing it (through amendment).
I think you missed my point. Of course they're part of the constitution, and I certainly said as much in that post, though in rereading I recognize that it was a little bit unclear what I meant, for which I apologize and I am going to quickly edit that right now.
What I Meant
Let me phrase it another way. I've found, tragically, that many people including Americans often think of the amendments, particularly 1 through 10, as
"the constitution" but the constitution, in total, is a much longer and in-depth document that defines the foundational structure of the United States government.
And it's useful to recognize the difference in the history behind the second Constitution 1787, and the 1791 Bill of Rights example. The first, the 1781 Articles of Confederacy, created a fairly weak federal government that was inadequately enabled, leading to the creation of the new Constitution, signed 1787, ratified 1788, and in force 1789.
The initial 1787 Constitution itself had a number of protections, and delegations of rights and liberties, but also he created a federal government that was much stronger, and it was not without opposition.
In order to ratify it, many states demanded that the Bill of Rights be added as amendments. The anti-federalists of the time
"feared the authority of a single national government, upper-class dominance, inadequate separation of powers, and loss of immediate control over local affairs." Sound familiar? Officially there were 70 delegates to the constitutional convention, several did not show up, and only 38 people signed.
While the Constitution created a stronger central federal government versus the failed Articles of Confederation, it was divisive, and two opposing political parties emerged almost immediately. The divisiveness has carried on for some 240 years. The first, second, third, fourth, and fifth amendments in particular, hinted at the fear people had of a strong central government.
This little tidbit of history I think is important, and it's one of the reasons why I like to point out the difference.