I have 2 suggestions:

1. show subscribed Communities first / top in list
2. show current selected Community's description, especially for the rules (but also to help identify which Community it was)

When we want to cross-post, its usually where we subscribed and interested into. So it makes sense to me to list them on top. Otherwise after clicking the cross-post, I have to open my profile to see the actual address of the Community again, to identify its address. As I am subscribed to more than a single Community with same topic, I also need to see the rules and its icon too, to make sure its the correct Community I want to cross-post.