I'm reading a book which is formatted like this:
-- No! said Gandalf, looking around. We must not go further before we have had a sip of the elf water! The old wizard looked very worried.
It's possible to "interpret" this if you spend enough time and effort, but it's anything but obvious where the "quote" ends and the narration begins. And I did not just make up an absurd example (although the content was made up); I see this exact situation repeated constantly throughout the book, and I've seen it many times before as well.
If using the (to me) far superior "quote style" format, it would be like this:
"No!" said Gandalf, looking around. "We must not go further before we have had a sip of the elf water!" The old wizard looked very worried.
Here, it's 100% clear what is being said by the character and what is the book's narration.
Before you say something like: "the whitespace/formatting makes it clear", this is just not the case. Perhaps this is due to my book being a pocket format, thus is made even more compact than a larger book would be, but they frequently have a character go on and talk for a huge paragraph only to suddenly "cut it off" with narration, with zero indication that this has happened. I always read it in my head as the character's voice until I realize it's switched to the book describing something again.
This style also means that basic punctuation marks are often omitted, such as in:
-- How can you say that, Frodo, Merry asked. The younger hobbit looked scared. Where would one hide such a dangerous ring?
Here, the question mark is not used, and it's not at all obvious whether the last part is asked by "the book" or by Merry. The correct (IMO) formatting would be (assuming that Merry did say the last part):
"How can you say that, Frodo?" Merry asked. The younger hobbit looked scared. "Where would one hide such a dangerous ring?"
No matter how I think about this, and how much I've attempted to like this "style", I just can't help but find it fundamentally, objectively wrong. It's not even that I "grew up with" the quote style. In fact, I actually saw this "dash style" much more commonly in the early books I read, since I'm from Sweden, and they seem to love to (almost) always pick the most silly way of doing things.
As far as I can tell, there are books of both styles here. I just don't understand who would ever prefer this confusing "dash style" (in lack of a better term). If I had written a book and somebody reformatted it in this manner, I would be very upset, even if it resulted in millions of more sold copies. I may make more money, but all those people would be experiencing it in a very sub-optimal and unintended manner.
Can somebody please tell me even just one pro side of this style? I don't find it easier to read, better looking, more "inviting", or anything other than just plain stupid. And again, I grew up with this style and have no reason to reject it simply because of not being familiar with it. I just can't see what possible reason anyone could have for preferring or inventing it in the first place, and I'd love to hear why it's a thing.
Usually, there is at least something which motivates an alternative approach, but in this case, I can't think of a single argument for this style -- only many against it.