I'd suggest the following major things:

• Commenters in threads to be colored by their first comment in that tree (if they first commented in red their username will be red the entire tree, that way it's easier on the eyes to distinguish who's talking), idea taken from a Reddit client I used to use ages ago
• I really don't like it when I'm on all and by mistake click on Android's Back button, it just moves me back to the community selection screen and doesn't let me get back to where I was in the timeline
• Highlighted search in the comment section of a post
• I'd love the ability to copy the URL to the attached content directly from the post

Also, I feel like clicking on a post frequently sends me to the attached content instead of into the post itself, maybe the post structure can be improved somehow?

Thank you so much for this awesome app and being so open to feedback