I think one of my biggest mistakes I think is that I didn't number the notes, which made it harder to know where to start, another one is that if you search a someone's first name without their last name you won't get anything (which makes sence irl, but I should have told the player so).
A general hint I'm gonna give is that all of the keywords are names. (people, places, etc)
Personally I don't think not numbering the notes isn't a big deal since there's only four and there's not a lot in them. I eventually did figure out that you had to search the full names, and got to what I think is a clue to decode the Damion note in his latest post. Unfortunately I'm not the best at puzzle solving so I got stuck there. Or maybe I'm overthinking it.
One mistake I've made in making my games is assuming the player will come to the same conclusions I did from the same information, so a hint that was obvious to me was confusing to the player. A general rule of thumb I've heard is that if it's a little difficult for you the developer, it's too hard for the player. I hope this helps!
