But isn't the central question ... whether even "law-trained persons" in 1776 shared a specific theory of capitalization, commas, or semicolons? Perhaps they did.They didn't. It was a matter of style or taste. Many of the Founders changed the spellings of their own names from one day to the next, and James Madison did not consistently spell the names of the delegates to the Constitutional Convention (an irritation for moderns using search tools to build concordances and indexes).
That is why one has to be careful interpreting texts, not just from the Founding Era, but for any era. Humans are sloppy. Don't look for consistency in minute details.
One example that illustrates the problem is the clause:
To define and punish Piracies and Felonies committed on the high Seas, and Offences against the Law of Nations;Moderns, or even many of the Founders (like James Wilson), tended to interpret "committed on the high seas" as an adjectival phrase modifying both "Piracies and Felonies", but piracy was not limited to the seas. There was a long history of land piracy, and "piracy" ("attack") should be understood, using more modern words, as "a warlike act by a nonstate actor against a country other than his own", to form a partition of warlike acts into state and nonstate acts, and distinguish warlike acts against one's own country as "treason". The clause should be read as having the phrase restrict only "Felonies" and not "Piracies", with a missing but needed comma following "Piracies" to make this clear.