It seems a few people prefer it on a girl. You say you're used to it, do you know an
Indigo? I was hoping because of the -o ending people would feel it was more of a boy's name. All my favourite -a ending boy's names, people seem to say "it sounds like a girl's name" or "it would be better on a girl" and that kind of thing. It seems it doesn't go both ways!
I love the nickname Indie too, though for a boy I'd probably write it
Indy.
Thanks!