When I first heard that John 3:16 was added at some point in time and that it was not in the original, I was a little sceptical. But after doing a little research on it, I find that it would indeed appear that it was added.
Please read and let me know your thoughts on it. Also let me know your thoughts about it and if there is anything that I should add to it.
Original New Testament (ONT)
(See Authentic New Testament). Footnote: While much that was in his documentary source (the Memoirs of John the Priest) has been adapted by the Greek author to bring the text into line with his ideas, as here, some passages, largely by way of commentary, stand out as his distinctive contribution. Whenever possible attention has been drawn to these, as in this instance, and some have been placed below the main body of the text and in slightly smaller type. The present passage is John 3:16‑21. [This passage has been so placed by the translator].
The Ferrar Fenton Bible Translation has the following in bracket indicating that the verse WAS ADDED BY THE TRANSLATORS at some point in time.
[For God so loved the world that He gave the only‑ begotten Son, so that every one believing in Him should not be lost, but have eternal life. For God did not send His Son to the world that He might condemn the world; but that He might save the world through Him…] and ends with John 3:21, Therefore it would appear that all the verses from John 3:16 forward to John 3:21 were added.