This is my favorite app so far. Love the swipe controls and the compact UI. Liking the snappiness of it all.
Ideas/requests
Add direct messaging (I can see my messages but can't respond to them).
Add trending communities when you click search/a way to explore communities rather than having to type in the specific community you want.
Make it so clicking on "all" at the top of the screen opens a menu that gives you the option to switch between all, local, subscribed and specific subs and functions as a search.
Allow user to customize UI a bit more, specifically in compact mode I'd like to be able to switch the side that the preview thumbnail is on.
Show profile banners and have a way for users to customize their banner and profile pic.
It would make more sense if you put your requirements on GitHub as an issue. It's best not to summarize everything in one, you can't work with that.
https://github.com/thunder-app/thunder