As I explained in this post, it would be nice to have a way to do the refunds, resent link, fix email addresses manually from our dashboard/purchases page (just exactly as the Humble Bundle customer tool).
Humble Bundle solved this problem giving each developer the possibility to give user support in its own times, right now itch acts like a bottleneck for user support. I'm not saying that, you are doing a incredible job (and sometimes it feels better if you can do the refunds/user support in your side), but when you get volume, you will be overflowed, and that will impact in the user support of all the games/tools. I think it's something to be considered in a future.
P.S.: I know that sometimes refunds can be used by bad actors to get a free copy of a game, etc. but sometimes it's a drawback that you have to accept (and sometimes when you get volume, the impact of these refunds is negligible).