I know this post is lengthy, but it's a bit of an insight into my mind as a multi paragrapher that can't respond well to very short posts. As you probably notice it's not just roleplaying that I write a lot in xD My English teacher scolded me once for writing way too much on an English assignment once. *Whistles innocently*
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For me it's extremely necessary to tell people that my partners should be comfortable posting 3 paragraphs or more. If we sometimes now and then have scenes where only 1-2 paragraphs are necessary for the scene and more is hard to write, then that's acceptable (which I also points out in my partner search). When people search after lengthier posts then the people that often write lengthier posts will understand what they're out after.
They're out after:
Body language
Location description (especially when they're moving around in a room or walking outside)
characters thoughts and emotions (memories if something triggers it)
Dialog
Other details (such as smell, background noises or something going on in the background which the characters takes notice of)
Just like when we're reading a book, we want to be able to see the world and feel that our characters and the other persons characters are real. Most people I have roleplayed with that write longer have gone very deeply into their characters psyche. With every word the other character says, their character have to process the words, react to the word (bodily and mentally), and eventually respond to the words (talk or action). It's also important to notice if something/someone close by are affected by the reactions or actions of the character. Like during a discussion on the street, if they start yelling at each other maybe people around them starts to turn their heads, mumbling to each other, the main characters might even hear some words and react to that.
In my experience when I've written with 1 paragraph writers, I don't get into their character, and I don't see their world. I barely know what their character is thinking or feeling, which can be good if you have an evil or manipulative character that's supposed to surprise the audience with a reveal that everything they did before was a lie, or if you have a character that can't feel emotions, but if it is the main character, then I want to know them more, especially if they have known my character from before the rp started since then that character will have to know things about their personality that I might not have gotten to know yet. Even if they don't show emotions often, they usually do feel emotions, people think more than they let others know, and that's what the reader (the other writer) want to know about even if their character doesn't know about it.
For me when I write an rp I am both a writer of my own book and I'm reading another persons book. If their writing doesn't appeal to me, then just like with a book, I get bored and stop reading. While the length in itself doesn't make a book interesting, the content does. And those extra details does a lot to keep my interest. Yes, there is a lot of differences between an rp and a book. Roleplays are more forgiving, we can make mistakes, we can forget stuff, there can be forgotten plotholes, or ridiculous solutions or coincidences that people probably would complain about if it happened in a book, and it's two people writing it to entertain one another (and possibly a small audience if someone else have decided to read it). And when two people are writing a story together, no matter if it's for fun or for work, it's important that the two have styles that matches (for the mot parts).
Sure there are people that can roleplay with exactly anyone without being bothered if the styles aren't the same, even if one writes ten paragraphs and another just one, one writes in first person present time and another third person past time. But most people I've met are like me. We want to have someone that can give as much as they get, someone that writes from the same perspective and time as them.
I like to write a lot, and I like to read an equal amount as that fuels my creativity. The less I get the more unsure I get on how my character should act. With less details about their character, the less I know my own character and what they would do. That's why length is just as important as quality for me.
Btw, I do not think it's bad to write between one line and two paragraphs, if you feel most comfortable with that, then go for it. There's a lot of people on iwaku that writes the same amount. So in no way am I trying to say that you're doing wrong or anything like that with this post. I'm just saying that it's not everyone's cup of tea. Just like some can't write more than a few sentences, others can't write less than a few paragraphs or a few pages. Keep to your comfort zone until you wish to leave it. Don't jump into an rp if you're not comfortable with the required length or lack thereof. If the story is incredibly interesting, but you don't think you'd be able to keep up with the posts, then you can always ask the GM if they're okay with you creating a similar idea out of their idea and put an easier/harder level on it.
Everyone have their own comfort zone, and their own ideal partners out there. If you're a person that has a certain style and wishes to play with others with the same kind of style, then it is important to tell people that 'this is what I'm expecting from you'. It might be irritating for people that doesn't write like that to see it all the time, but even I have to turn my head from plots I want to join because the person writes in a way I know I can't handle for very long. I know I would get bored and eventually not know what to write. It has happened a lot of times, and with time I've learned that I have a certain style and to spare both myself and my future partners from a short lived roleplay, I should just tell them what I want, and not join in on something knowing that they aren't comfortable writing in my style and I aren't comfortable reading theirs. In the end, those types of matches will go to the roleplay grave quickly.
(Note: I'm mainly talking about one x one as that is my favored type of rp. But even in group roleplays I do prefer lengthier posts, though I don't mind shorter posts on a more regular basis if it's a big group with much more characters to take in.)
Phew, I think I'm done. Sorry for rambling ^^' I'm bad at containing myself.