Yeah! So using Jacksepticeye's lets play for time stamps, you can see that the writing changes around 1:13:00 - Note the lowercase a's are very different, and the font overall looks like Sam's.
Font throughout most of the game:
Change around 1:13:00:
And Sam's journal to compare handwriting:
Interested to know more! Also, I meant to say - Absolutely love the game! It was hard to tell the twist at first, but once you really got a feel for the different voices it all made sense! It made it all so satisfying. Thank you!!