Funny punctuation differences!

Alright, disregard what many might think, punctuation between spanish and english actually differs in ways that seem too dumb to exist, but they do anyway.
In this case, I'm not talking about commas, periods, full stops and all those funny guys that pretty much all languages use the same way, but I'm talking about the use of em dashes and quotation marks.

You see, a loooong time ago, when I was at elementary school (and whenever we had Spanish classes and literature and writing and all that mumbo-jumbo on middle school and even high) they taught me something that english speakers find a huge punctuation error.
Dashes (long ones, apparently called em dashes) are usually used for dialog. To write dialog, you write the dialog between those funny-looking hyphen-like dashes (although there are other ways to indicate dialogs using them in even weirder ways).
So, if I was writing a dialog using spanish grammar I would write something like this in most cases.

The killer potato rolled up to Scootaloo and, in front of the terrified filly, it said —You're dead chicken meat now!— sporting a long evil grin on its tubercle face.

However, in english that's a big error. From what I've been reading on books and articles lately, in english you can pretty much only use quotation marks in most cases.

The killer potato rolled up to Scootaloo and, in front of the terrified filly, it said "You're dead chicken meat now!" sporting a long evil grin on its tubercle face.

Of course, I'm kinda sleepy right now and I'm sure there's some actual grammar mistakes on what I just wrote as an example.
Regarding quotation marks, although they are used in spanish in very few instances to write dialogs, they are mostly used to write thoughts of characters, to point out a word you want your readers to focus on (disregard if it is because the word itself is improper or just important) or just to quote something somepony else said/wrote.
Also, one last funny thing I must point out is, in spanish you can also use ‹‹›› as quotation marks.

Let's explore the killer potato example a bit more to put an example.

"Fried chicken with french fries...? Such an ironic way to die you're about to have, Scoots!" thought the filly as she backed away from the killer potato. —I-I'm not dead yet!— she yelled.

So, that there is why my punctuation is "off"... since technically is off for english, but in spanish it is perfect, too bad nopony taught me that little difference before. Oh well, guess I'll just have to correct that.

tl;dr version.
In spanish you use em dashes for dialogs instead of quotation marks. Also, you use quotation marks for inner thought and pointing out words. Didn't know in english they didn't use punctuation that way, that's why my grammar and punctuation is off.