[haguruma]

Originally Posted by Renall

This is actually one point where I wonder about whether that's a screw-up for exactly that reason. Even if we assume that the letter was maneuvered in such a way that Natsuhi was likely to find it first, how could it be known whether or not she'd read it on her own and immediately leave? What if she decided to share it or read it out loud? Also, when did that letter even get written? Does Beatrice carry stationery around?

Well, basically we can say that at this point it doesn't matter whether Natsuhi reads the letter or not, it's another "leave it to chance" game of which Yasu does a lot. The bomb was already set, so Natsuhi will die one way or the other, it's just the final chance for Yasu to maybe get revenge.
Scenarios like these are possible:

• Natsuhi doesn't read the letter and later dies in the explosion
• Natsuhi reads the letter but ignores it and later dies in the explosion
• Natsuhi goes with other people, she is shot and the other people die in the explosion
• Somebody else reads the letter and goes, so Yasu has no reason to show herself and everybody dies in the explosion
• etc.

Also, the manga for EP8 implied heavily that Yasu was very much torn about her emotions towards people like Natsuhi. On the one hand she wants her to be the mother she never had, but on the other hand hates her for all that she caused (the raging culprit-shadow in one panel was pretty clear on that).

Spoiler for EP8 Manga Panel:

Originally Posted by RandomAvatarFan

After watching through EP4, I realized that they said that one of the bottles was found on the island, and the other was found at sea later by the fishermen.

Yet, EP1 ends with the bottle being found five years later.

I was a big proponent of Bottles = Episodes, but now this makes the ending to EP1 make no sense whatsoever.

I don't know where you see it not making sense, but maybe I am overlooking something.
It was said in the Endroll part of EP1 that a message bottle was found several years (not 5 years, don't know where you got the number from) after the incident by a fisherman on a nearby island adrift in the sea.

This message bottle was released to the public, by that fisherman, after Eva sold Kinzo's library from Kuwadorian via auction and the interest in strange and occult items from the Ushiromiya household rose. The fisherman probably saw a good way to make money and went public. This could likely have been the bottle that contained EP1.
As a reaction towards this the police also released the bottle they found, which they had probably filed after they had somehow ruled out the likelihood of what they found in their message bottle. Or maybe there was information back then, but nobody actually cared, as Ootsuki said that up until Kinzo's library was released only very few people held interest in the case. This bottle could have been EP2.

So where does it make no sense?

Originally Posted by GreyZone

I think what we see in the story is just the interpretation of someone from 1998+ (Yukari, Tohya, Ikuko or others). The "reader" may change at some points though and possibly add their own interpretation or even knowledge into the story (or perhaps there can be multiple readers at once, which explains the "chaotic" nature of EP8).

I am also a proponent of this theory, considering for one the things you already pointed out, but also what was already said in EP1's Endroll, namely that during the occult craze several people started adding their own interpretation to the story found in the message bottle, even adding cruel and fantastical elements to it.

There is also the short exchange between BlackBattler and Ronove in the TIP Forgery No.xxx where upon the question when they had last met Ronove gives a cryptic answer that it should have been Trinity of the Golden Witch but considering that "Lady Bernkastel's gameboard is considered to be the last" (EP7?) they would have to say that this one was the last. Yet on the other hand they remark, no matter when they last met, they still have just met a moment ago.
This also shows that the metaworld may not work under the same logic of time and space as the world of 1998 does. It is merely given "an order" by the way it is regarded by those who give order to that world, which would be the Spectating Witches. This is impossible if the meta was actually part of the actual narrative, because then it would be bound to the respective order it was written in.