I understand what you're saying, however, since this is a member zone, users are moving back and forth between pages. So the cached combined css and js does have a positive impact on speed.
In Comet Cache, there is an option to force caching even when a Nonce is present:
Cache Pages Containing Nonce Values in Markup?
This should almost always be set to Yes. WordPress injects Nonces (numbers used once) into the markup on any given page that a logged-in user lands on. These Nonce values are generally used to improve security when actions are taken by a user; e.g., posting a form or clicking a link that performs an action. If you set this to No, any page containing an Nonce will bypass the cache and be served dynamically (a performance hit). Even the Admin Bar in WordPress injects Nonce values. That's reason enough to leave this at the default value of Yes; i.e., so Nonce values in the markup don't result in a cache bypass. In short, don't set this to No unless you know what you're doing.
I have set to: "YES, For Logged In Users, Intelligently cache pages containing Nonce Values."
However, JS and CSS are still not combined and compressed when a user is logged-in.
I also tried installing Come Cache on a virgin wordpress site, with no additional plugins, and the problem persists. When a user is logged-in, the same issue is present.
I am wondering if this is a bug?
Where can I report bugs?