mf

I think this is a very good question, and you came up with a really interesting answer/related thoughts, and it sounds like you've hit on something very useful and insightful. As evidenced by the fact that I (like marginaliana) have been pondering this for days and struggling to answer it, it's not that easy to figure these things out!
In fic-writing, I feel like for the most part I am pretty shameless - I guess my attitude is I write for myself first and foremost, and if anyone else likes it that's a bonus. But actually, if I scratch the surface, I think I'm scared to write/post things that give too much of myself away. I have some kinks that I'm not totally comfortable with, and I have written about them, but usually coming at them obliquely - tweaking some of the elements so that it's not too close to the truth of what I really enjoy. So, if I'm not misusing the term, I guess I'm scared of writing/posting id-fic? Not sure why - I don't expect to get flamed for it or anything. Maybe I'm convinced that what I like is so weird that nobody else could ever possibly enjoy it, so it'd be unforgivably self-indulgent for me to post it? And/or maybe I'm scared of making myself that vulnerable (pretty sure that's a broader problem I have).
In general, oh, tons of things scare me XD Anything that involves spontaneous human interaction where the other person might react with the slightest hint of disapproval, for a start :P despite how a lot of the time I might come across as shameless. Kind of similar to you, I spent a lot of my formative years constantly receiving messages that I was 'weird' - how I dressed, how I acted - and so I took the can't-win desensitized attack-as-defence approach of just embracing it and saying fuck the haters. Which works great with actual haters, but leaves me kind of at a loss for how to deal with, well, just neutral parties...