Absolutely. When I first started in fanfic, I was so new, I didn't realize that a lot of people didn't like OCs, or even what the term Mary Sue was. I created one for my very first story, because I wanted a love interest for Giles and honestly, I was never going to ship him with any of the girls on Buffy at that time. Because I write long, plotty fics, too, I needed bad guys. I hate demonizing characters, so the easiest way most of the time was to create an original character that I could kill off. That still sounds logical to me.
I've never actively thought about Mary Sues, to be honest. My goal is to try and make characters as well-rounded as possible. Flawed like real people. I might not always succeed, but I do try. It's impossible to say "don't self-insert" because, well, I believe most authors do that. What is writing but putting your imaginary role playing games into words? I'm not saying it happens all the time or that you choose a character and relate to them. But I'd like to think authors relate/understand their casts. They give them habits the author has. They share likes. They might have a character react in a way the author would. That kind of thing. That for me is definitely a form of self-insertion, and is pretty much inescapable.
The trick is not to idealize. Everybody has flaws. Everybody has enemies. Don't forget those. Or give them purple eyes. ;)
9 – Pairings – For each of the fandoms from day two, what are your three favorite pairings to write?
10 – Pairings – Have you ever gone outside your comfort zone and written a pairing you liked, but found you couldn't write, or a pairing you didn't like, and found you could?
11 – Genre – do you prefer certain genres of fic when you're writing? What kind do you tend to write most?
12 – Have you ever attempted an "adaptation" story of a favorite book or movie but set in a different fandom?
13 – Do you prefer canon or fanon when you write? Has writing fanfic for a fandom changed the way you see some or even all of the original source material?
14 – Ratings – how high are you comfortable with going? Have you ever written higher? If you're comfortable with NC-17, have you ever been shocked by finding that the story you're writing is G-rated instead?
15 – Warnings – What do you feel it most important to warn for, and what's the strangest thing you've warned for in a story?
16 – Summaries – Do you like them or hate them? How do you come up with them, if you use them?
17 – Titles – Are they the bane of your existence, or the easiest part of the story? Also, if you do chaptered story, do you give each chapter a title, or not?
18 – Where do you get the most inspiration for your stories (aka "bunnies") from?
19 – When you have bunnies ideas, do you sit down and start writing right away, or do you write down the idea for further use?
20 – Do you ever get bunnied inspired from other people's stories or art in the same fandom?
21 – Sequels – Have you ever written a sequel to a story you wrote, and if so, why, and if not, how do you feel about sequels?
22 – Have you ever participated in a fest or a Big Bang? If so, write about your favorite experience in relation to one. If not, are there any you've thought about doing? And if not, why not?
23 – When you post, where do you post to? Just your journal? Just an archive? Your own personal site?
24 – Betaing – How many betas do you like to use to make sure there aren't any major flaws in your story? Do you have a Beta horror story or dream story?
25 – Music – Do you listen to music while you write? Do you make playlists to get into a certain "mood" to write your story? Do you need noise in general? Or do you need it completely quiet?
26 – What is the oddest (or funnest) thing you've had to research for a story?
27 – Where is your favorite place to write, and do you write by hand or on the computer?
28 – Have you ever collaborated with anyone else, whether writing together, or having an artist work on a piece about your story?
29 – What is your current project or projects?
30 – Do you have a favorite story you've written? What makes it your favorite? And don't forget to give us a link!