Unfortunately, you have a theme that is heavy handed with it’s css and is forcing it’s style over the BP css. Theme compatibility is working it’s just that your theme has css that is styling the BP markup in an unflattering light.
Theme compatibility is not perfect. It’s main goal is to get BuddyPress inside a WordPress and function. How it looks can rely on the WordPress as in your case.
You will need to change some of the css in your theme to fit BP inside better.