Cosplay is a large part of my life, and about the same time as I started cosplaying is when I began to discover that transgender people exist and realize that I was one. None of the environments before were anything like cons, even the very small first one I attended. I didn't even know about binders, and through a crossplay panel is how I learned about them. I wasn't wearing one at my first con, but I still got addressed as the character I was cosplaying and male pronouns were used and I just felt so at peace and happy, glad that even with my poor tries at first costume people could still recognize who I was cosplaying.
I did acquire a binder before cosplaying next (this was in an area where cosplay was very prevalent, so there were small gatherings in costume every other weekend) and I wore it with my partial cosplay out in public on my way to the event. Normally I blend in with the background, but in San Francisco area it seemed safe enough to appear somewhat out of the ordinary. On these excursions I would sometimes be asked by strangers for directions, and I had a few who saw me as a guy with my new found binder and I was like 'huh, that felt right and kind of amazing'.
Generally conventions have been very welcoming places for me, and I have made some awesome friends through going to those. I appreciate that it is common to address a cosplayer by their character's name and pronouns, so most of the time that avoids getting misgendered if you are cosplaying from the gender that matches your identity. It still happens when they will bypass who you are cosplaying and just address you with what gender they think you are. When it does happen its a downer, but its still less frequent when out in general public.
I am still very self-conscious about how bulgy my chest is even when bound, but I don't let that stop me from cosplaying characters that I love and relate to.
