Hello Muffin,
I hadn't responded to your question because I figured it would be a waste of readers' time to see an "I don't know the story you're talking about." If I had known it, I would have posted.
You are right; this is a very welcoming group, and it is very gentle with newbie fiction writers. I know -- I speak from personal experience. Prior to joining this group earlier this year, I had written almost no fiction before. I have found that the group as a whole is very positive in the feedback that is left. Pretty much everyone here subscribes to the "If you can't say something nice, don't say anything at all" philosophy. But if you specifically ask for constructive feedback, you will probably get some helpful, gently phrased, advice.
The one piece of advice I would give you now: If you do decide to write some fanfic, ask for a beta reader (BR) or two (or three) to look over your story and give you suggestions before you post it. Pretty much every author I have communicated with -- from complete newbies to multiple-award-winners -- has stated how valuable their BRs' input proved to be. I know that my own stories would be much the worse without my BRs' feedback.
We are always eager to read fanfic from new authors. So if your muse offers you a story, by all means write it up!
Joy,
Lynn
