There are at least two "Diaries" found on ABCs Webpage, so they are official: Actually they are both parts of one diary, that originally belonged to Janelle and then was found and continued. What happened to Janelle is unclear, but the last entry raises fears that she was either taken or is dead.
The two parts of the diary
The second part starts with the words "found this diary on the beach..." and is obviously written by someone who is not a survivor of the crash, but also seems not to belong to the group that is commonly referred to as "The Others". The existence of the stations was unknown to him prior to the opening of the hatch. Despite all this he or she is living with the survivors. In one line, the survivors are referred to as "the others". The diary may also hold hints on who it is, since the writer is present at several events (like the arrival of the tailenders), so he may appear on screen in those scenes. If you follow the pages, there is a link missing - continue reading here.
Thoughts about the (second) writer:
- Doesn't seem to be either one of The Others or one of the crash survivors, since s/he talks about them with a distance.
- Lives on the beach with the other survivors - it can be assumed that the writer's name was on the flight manifest as this was checked by Hurley.
- Might be the brother or sister of Henry Gale or someone else who would call him "my brother".
Note that Desmond calls Jack "brother" a few times, so this might not be a term referring to actual family relations.
Note also that it is also possible, that this is a misunderstanding, since the writer never has seen "Henry" in the Hatch. Maybe s/he only assumes that it could be his/her missing brother?
- Is assigned a shift in the hatch. Later confronts Locke demanding to be let in to see "my brother".
- Is not very fond of religion, civilization or people in general.
- Talks about the group being a microcosm of society.
- Displays a great deal of curiosity for the survivors talking in a way that makes it appeas as s/he is not part of their group.
- Talks about an upcoming war/conflict on the island without specifying the opponents and is at the same time afraid of the consequences and all the killing.
- Cannot be one of the "tailies" (nor Michael, Sawyer, or Jin) as the diary talks about their arrival.
- The first writer was someone that didn't appear actively in the show, it's a reasonable assumption that the same would apply for the second writer.
- The second Writer confirms that Mr. Eko and Charlie are building a church, and mentions "losing their mind".
- The second writer's sentence "But if we wish to live in peace on this island ever again..." may indicate that this person, and the others like him e.g. Henry Gale, lived in the island before the plane crashed.
- Shouldn't be written by Rose as she is always doing laundry and doesn't seem bothered by the hatch, the writer is dumbfounded by people doing laundry in the hatch.
- Can not be (since these are mentioned in 3rd person or do not fit otherwise):
- Could possibly be someone with a dissociative mental problem like "multiple personalities". This would also explain the seemingly distanced writing.
- Apparently the diary is now missing pages. Especially the pages that contain the information about the author demanding to see "his brother".
- The Diary is written by Libby - who could be someone with possible "multiple personalities" (her appearence in "DAVE" at the end - freeky). She has not been mentioned in 3rd person.
- The Diary could be written by Bernard, considering the author's extreme resistance to staying on the island and the interaction with Mr. Eko and Charlie, where they ask if the author wants to help them build the church, which happened to Bernard in the episode "S.O.S.". Also in that episode, Bernard mentiones the crazyness of making a home on the island (like Rose "building a kitchen") - that has the same undertone as the Diary which talks about people beeing crazy because they are doing laundry.
- The second writer says "We of course are taught to understand the vital importance of children". This statement can create the impression that this person belongs to some special family of human beings, different to the rest, perhaps the result of a medical/social research program conducted by the Dharma Initiative to create some new better society. The fact that he refers to Henry Gale as "brother" could indicate the fact that they are both members of this family who live on the island. This person's comments about children show that he has no real experience with them, as if he first saw children when the survivors arrived. This could mean that members of this society on the island cannot reproduce, a problem that The Others are trying to tackle with their medical experiments on pregnant women, which also explains their general interest on children. His comments about human beings and their behaviour overall could be based on the fact that he/she had no previous real exposure to people outside the island. It is also clear that this person does not know about the hatch and the other labs on the island or the true nature of The Others he calls "primitive people". Perhaps the "others" in the labs are the creators of this society on the island and they control and monitor them in secret while engaging with them dressed as primitive people only.
- May be a distraction ploy. Could keep us reading so much into the Journal that we miss things very clear.