The ability and willingness to edit and rewrite, sometimes aggressively, in service of the story.
A good writer understands criticism and doesn't bark whenever they get negative reviews. Also someone who's able to improvise on the spot.
I think it helps to have lived a little & also maybe to be unafraid you'll appear uncool. When I tried to write in high school it sucked. I now think maybe it was because I was only trying to imitate what I'd read. I hadn't had enough experience with letting my own feelings out to be able to invent characters who could put them into words.
I think something that's tangential to things brought up so far is you need to be willing to experience. It's good to have your comfort zone of things you like, but be willing to read things outside that zone, experience things you might not normally go for. It's just as important to understand what works for you as well as what works for others.
Example: I don't like romance, it doesn't do much for me, and I have no interest telling those stories. There's nothing wrong with that but I understand that those kinds are stories are ones others want to tell and want to read. By reading those kinds of stories, talking with others about them,and learning what people see from those stories helps me write better character relations,even if not romantic relations.
I think traits of a good writer are inseparable from traits of good writing. Even if you're unwilling to take criticism, or closed off from new experiences, or have a big ego or look down on others (the latter two are different traits btw), you can still write a sincere, evocative, tightly woven, well paced story with likable characters and that makes you a good writer.
There are correlations, of course (for instance, someone who's unwilling to take criticism is more likely to write something incoherent and adhering only to whatever they're feeling are at the moment instead of some focused direction), but it ultimately still ties to the traits of a good story. In general, I like separating the creation from the creator :]
Someone who is willing to put in the work to finish a story and is willing to improve it for the better.
There are a lot of people who want to be a writer, but it takes a lot of self discipline to see that vision to the end especially if it's a big project. And often it doesn't end there- there's a lot of editing and improving that can be achieved if a person is willing to look at their own work critically.
Self-critique is very important in my opinion.
Yeah, I think you listed two pretty important ones: criticism and lived experiences. As a note about experiencing life, I don’t think necessarily means traveling the world or trying everything once. Rather, I think as we grow older, develop passions and careers, we learn how the world works and how people behave. I think this is important for developing characters and a world that feels “real”. Understanding how laws, money, and businesses work is important for understanding how to make realistic variations of those societal rules.
I super agree with this answer! 
🏻 Absolutely empathy is important. Unfortunately this usually requires talking to people, which usually requires putting on pants and leaving the house, so that sucks. 
Omg yes!!! I had this revelation a year ago that transformed my writing. I realized I shouldn’t try to create this perfect, “good” book that followed all the rules I’d learned and copied the greats (according to me greats at least). I just decided to write what I thought was fun to me and it frees me from this stress of being “great”. Now I just try to write something that I enjoy reading and it usually works out alright.
A good writer never loses sight of the purpose of what they're writing.
If they write advertising copy, they understand that the aim is to highlight the best features of the product to the specific sort of audience they're aiming for.
If they write literary fiction, they understand that they should create a powerful experience that makes people think and show off their mastery of the written language.
If they write popular fiction, they understand that they should use accessible vocabulary and write a short, tight story that delivers on the expected tropes of the genre they're in and entertains the reader.
Bad writers get too wrapped up in themselves to think about the audience. They'll let their favourite scenes drag on and waste the reader's time to indulge themselves, they'll use inappropriately fancy vocabulary to show off how clever they are and exclude ESL readers on a popular light fiction focused platform with international readers like Tapas and when people don't read their work, instead of looking at whether what they're making and how they present and market it is appropriate to the audience, they blame the audience like, "Oh, they just can't appreciate my art because they're too stupid!" or they blame the platform like "Hmph! Tapas is trying to hide my work because it's too clever and challenging!" It's all about me, me, me.
Hmmmm.... based on my experiences working with writers:
They respect the artist as the other half of the storytelling duo and know when to hold off adding dialogue or narration and just let the art do the talking. They listen when the artist makes suggestions about panelling, character design or other areas where the artist is probably more experienced, instead of treating the artist like an art monkey who just illustrates their amazing words. Oh and they don't think their name should be the only one on the cover.
They use clear, consistent formatting for their scripts. Doesn't need to be industry standard, just easy to follow.
They have studied panel layout and visual storytelling so that even if their drawing isn't the best so they'd probably never be an artist, they don't try to dictate the panelling to the artist while clearly not understanding how panels work. So they don't try to fit things that ought to be 2-3 panels into one like "John enters the room and sighs as he drops his briefcase, noticing the smell from the kitchen," or put a complex establishing shot on a page that has 7+ panels on it.
They don't put too much text per panel or speech bubble. They understand that a sentence or two is enough, and that more writing doesn't equal better writing.
Very good answer again, especially point number 3.
A good comic script writer has to understand comics, know about storyboarding etc.
and has to empathize with the artist who is reading the script
I’ll just try to mention something I haven’t seen mentioned yet: a daily writing schedule. I read a book a while back that just described the work habits of famous writers and artists and it didn’t surprise me to see that most of them (in all categories of creatives) maintained strict working hours. Even some of the outwardly chaotic and artsy seeming still maintained a very orderly work flow. It was actually kinda rare to find one that was like “I write whenever the muse strikes me.” A lot of em were more like “I write every morning no matter what.”
An article: https://jamesclear.com/daily-routines-writers
The book I read: https://www.masoncurrey.com/daily-rituals
This one is big for me. Writers should be willing to teach but also teachable. I've seen SEVERAL writers who aren't necessarily "popular" lord over newbie writers the number of books they've written and their USA Today Best Seller title. They don't mention that that title was earned because they managed to sell a certain number of books.
Bit of a disagreement here with the mastery of the English Language. If you're talking about writers in English speaking countries, yes, but what about France? China? Italy, Brazil, etc. Also, education is not a prerequisite. Samuel Clemens, aka Mark Twain wasn't educated beyond grade school.
to me a good trait for a writer to have is serving the story. They, the writer, comes second, you don't think about yourself or how people will want to meet you or what people will think of you. You want them to want to meet your characters, to know more about them, to think about them, not you. You're just a sidekick who's along for the ride. You're always thinking: will this turn of events serve the story, will it further it, will it flesh it out more. If I change this will it lessen the impact of what happens to the characters or will is strengthen them. It's all about the story.
For me, what really separates a good writer from a bad writer is the element of respect. These writers respect their readers as human beings and their characters as human beings, too. Good writers are usually straight to the point, too.
I think I have a short list of traits I can think of.
Self awareness- the ability to not only understand ourselves in reality but also how our mindsets feelings and experiences control what and how we write.
Dedicated- Anyone can be a writer, but you're not an author until you finish an actual book. It's not always easy but we have to push ourselves to work and eventually complete our work.
Creativity- so many people think that Creativity is the ability to make anything, but I'd argue Creativity is the ability to make something good while working under restrictions and guidelines. Showing that you can craft a world with rules and keep your characters restricted to those rules while telling a good story is something I feel a lot of people struggle with.
Confidence- It's easy to write a story about something controversial like race, sex, politics, so on and so on, but you need Confidence to actually present that story to the world.
Self motivation- there is no guarantee that your book will become popular. Yes, you should probably write for an audience, but commit to finishing your projects for you first. You need the strength to put out book after book regardless of whether or not anyone is reading yet.