I grant this work to the public domain. Although no one can prove anything, I agree with the position that the Codex Sinaiticus is a forgery, or at least a nineteenth century copy. It is a story that involves human nature, human ego, human pride. The forger was Constantine Simonides, highly knowledgeable and skilled in calligraphy and paleography, who was eventually found to have forged many works that he had offered for sale. Sinaiticus was created by him in 1839, when he was nineteen years old. What he really intended to do with it we don't know, as we cannot trust his explanations of his intention for it, being a forger. But this does not matter. Somehow, this manuscript, or at least parts of it, ended up in a trash basket in St. Catherine's Monastery in Egypt. Constantin von Tischendorf found it there in 1844. Tischendorf assumed that it was of great value and antiquity, and as that subplot developed, those in the monastery changed their tune about its being trash and began to deal with Tischendorf as if the manuscript was valuable, ultimately contradicting Tischendorf's testimony about finding it in the trash. As the saga developed and both the manuscript and Tischendorf gained notoriety, Simonides found out about it and began to contest it in 1862. Again, this is where human ego and pride come into play. A key question is that of incentive. Simonides had no incentive to falsely claim that he wrote it, since this would implicitly testify to his being a forger, and that of a Bible manuscript, no less. Nor was there any money to be gained by him. Indeed, he had nothing to gain and much to lose by going public about it. And this is a point that I think is missed. But Tischendorf, also a man known to have an ego, and who received funding for his ventures, was now gaining fame based on Simonides' work. And this would certainly be expected to irk Simonides. But Tischendorf, and Henry Bradshaw, the well-known British librarian, had already dug their heels in and were not to be humiliated. The end result was as we now know, and contemporary academia of the WH/NA tradition is not willing to concede to such an embarrassing proposition either.
So, what does this mean for us, especially since this, along with Codex Vaticanus, are the prime manuscripts used for many modern translations? First of all, Simonides, being a highly skilled forger, would not have changed the text, even if in a work of forgery, such as to cause contention that would easily bring into question its authenticity or claimed antiquity. Therefore, we need not be concerned about some heresy or false teaching within its pages. In fact, he had to have been compiling it from legitimate New Testament manuscripts. He certainly neither back-translated it nor had memorized the Greek New Testament. So, in that sense, it is a legitimate, hand-copied manuscript, just not an old one as claimed. Even F.H.A. Scrivener's 1894 Textus Receptus is a Greek manuscript compilation, a work of textual criticism, reverse-engineering the King James 1611 manuscript basis, as is the Nestle-Aland text a compilation based on select manuscripts, or even Ivan Panin's peculiar 1934 Greek text, compiled based on recognizing numerical patterns that he was convinced were so remarkable as to distinguish one variant reading and discard the other. None of these compilations are copies of any single ancient manuscript, and none were motivated by a desire to actually alter the Word of God. I myself am currently in the process of translating the New Testament from various manuscripts, using the NA28 with Critical Apparatus, Robinson's Byzantine text, and Scrivener's 1894 Textus Receptus, examining all manuscript discrepancies in every verse, and have found nothing alarming or remarkable corresponding to references to Sinaiticus; I just don't give any weight to the ℵ designation when I see it cited in variant readings. Simonides did a highly skilled job, even if the intent was forgery, and we don't know if that was even the intent. However, my suspicion, though subjective, from examining every variant reading, is that it was a forgery, but perhaps after strategically planting it in a number of places, ready for him to "discover" it later the same way Tischendorf did, he abandoned the idea, perhaps because he knew he was messing with the Word of God; but, again, his thought process would be my guess. The reason I would assess it a forgery, besides that he was forger by profession, is that I see that there are many places where it varies in ways that are unique but of little to no consequence, as if Simonides was trying to make it unique, but not deviate so much so as to cause suspicion. Codex Bezae, for example, by contrast, is far, far more discordant, leaving us to wonder whether it is due to intentional embellishment or imperfect reconstruction, but in any case we could never translate the New Testament solely on its witness. So, in the end, I assess that Codex Sinaiticus is of no consequence to Christian doctrine. It is just that it isn't one of the "oldest and most reliable manuscripts available," as that political camp of textual criticism claims, and I wouldn't grant any weight to it as a basis for New Testament translation.
My conclusion that he is the author is based on abductive reasoning, of course, but so are the conclusions of those who claim that it is "oldest and most reliable," as well as pretty much every individual text critical choice and justification made of any variant reading between the various manuscripts, whether by the likes of Erasmus and reformation-era translators, the likes of Tischendorf, the likes of Scrivener, or of any modern textual critic.
I grant this work to the public domain.