You seem to be in the habit of posting long cut and pastes without attribution. I see this one comes from the "Federalist Blog" you "left" in passing. Not very good form, Chilly...

But very well ...

The question was what "common understanding" the framers may have had of the term. You suggest, with no proof whatsoever, that it was based on the writings of a Swiss philosopher. You dismiss the possibility, based on contemporaneous evidence, that the framers' understanding may in fact have been based on the broader British common law adopted and applied in the various delegate states. For instance:

It thus clearly appears that, by the law of England for the last three centuries, beginning before the settlement of this country and continuing to the present day, aliens, while residing in the dominions possessed by the Crown of England, were within the allegiance, the obedience, the faith or loyalty, the protection, the power, the jurisdiction of the English Sovereign, and therefore every child born in England of alien parents was a natural-born subject unless the child of an ambassador or other diplomatic agent of a foreign State or of an alien enemy in hostile occupation of the place where the child was born.

III. The same rule was in force in all the English Colonies upon this continent down to the time of the Declaration of Independence, and in the United States afterwards, and continued to prevail under the Constitution as originally established.

United States v. Wong Kim Ark (1898) 169 U.S. 649

Next, if you're going to cut and paste someone else's work, I suggest you include the entire context. This is especially evident in your truncated bit about "dual allegiances." Here's what the Federalist Blog-ger actually said:

The British doctrine allowed for double allegiances, something the founders considered improper and dangerous.

Framer Rufus King said allegiance to the United States depended on whether a person is a “member of the body politic.” King says no nation should adopt or naturalize a person of another society without the consent of that person. The reason? Because “he ought not silently to be embarrassed with a double allegiance.”

That's it. That's the entire reason this guy thinks the founders considered dual allegiances "improper and dangerous." Of course you'd think the guy would've been honest enough to point out that the Rufus King piece to which he refers was not written during the drafting of the Constitution or even the debates over its ratification, but was written in 1794, seven years after the Constitution was drafted, and five years after it was ratified.

You'd think he'd also be honest enough to put the quotes in their proper context. Like this:

The social Contract converts the several associates into one moral Person - or Body Politic. This personage is composed of the contracting parties; it continues by a succession by Birth and by additions by adoption or naturalization; to whom allegiance is due I don't enquire; I ask is AB a member of the Body Politic? In reason every such addition supposes a renewal of the contract between the Body Politic and the adopted member - the consent of both parties is requisite. All persons are in legal contemplation members of some one nation; this relation continues until they are adopted or naturalized by some other nation: no nation except in peculiar instances adopts or naturalizes without the request, much less agt. the will, of the member of another society; some formality which is individual and express accompanies. A citizen is bound by Duties to which an alien is a stranger; he may not have them required of him without having consented to become a citizen, he ought not silently to be embarrassed with a double allegiance in short no doctrine is less supported than that which teaches that a nation may at their Pleasure adopt the citizens of another nation without their Consent or application-it certainly goes too far.

Besides this doctrine is not only novel and unreasonable but against contemporary exposition and indeed is repugnant to laws wh. may fairly be deemed declaratory of the meaning of the article.

The Life and Correspondence of Rufus King , p. 536

http://books.google.com/books?id=9GEsAAAAMAAJ&dq=%22member%20of%20the%20body%20politic%22%20%22rufus%20king%22&pg=PA536&ci=220,176,735,720&source=bookclip

Wow, wonder what got Rufus King so riled up? Conferring natural- born status on the children of aliens? Uhm, nope:

By the construction insisted on every foreigner who before the new constitution and after the adoption of the Confed. came into this country and resided here a term, though not exceeding 8 months, became a citizen of the US. To such who did not desire this character such a law would be embarrassing - to those, on the other hand, who did, the law would prove highly convenient, since no expence, trouble, delay nor oaths were required; while a provision so extensive, and so easily and economically to be employed was in existence .

Ibid.

So maybe you should research other people's stuff before you cut and paste it. Otherwise you just end up looking silly, Chilly.

Oh, and that "perpetual allegiance" stuff? Your blogging friend is wrong if he really believes that under British common law allegiance "could never be severed or altered by any change of time or act of anyone." Maybe he should have read a little Blackstone:

Natural allegiance is therefore a debt of gratitude; which cannot be forfeited, cancelled, or altered, by any change of time, place, or circumstance, nor by any thing but the united concurrence of the legislature. William Blackstone, Commentaries 1:354, 357--58, 361--62

But sure, it was a doctrine the founders didn't care for at all, and they made sure to repudiate it loud and clear. Hint: Declaration of Independence.

On the other hand, Congress HAS concurred on the manner in which United States citizenship can be renounced. Sort of like what Blackstone described.