We've use Pivotal Tracker before, and it always felt challenging to have more than a basic description/discussion (maybe that's the point), but most tools like Jira, Github Issues, Trello, etc, facilitate a larger view.
One of the basic notions in the school of thought that Tracker comes out of is that team interaction is valuable and to be encouraged. So making a tool that makes it easy for people to not talk undermines the broader goal.
One of the basic insights of the Agile movement (R.I.P.) about Waterfall is that processes structured around documentation rather than collaboration have a lot of subtle bad effects that gradually destroy characteristics you'd like your teams to have. E.g., responsiveness to change, systemic effectiveness, resilience to failure, low overhead, ability to ship frequently, ability to deliver customer value.
That's why when I set things up I generally drive things off of index cards. [1] Those are obviously insufficient, which forces people to discuss and collaborate. (That's in contrast to more voluminous documentation, which is subtly insufficient.)
Tracker is very opinionated and is deliberately trying to not be the be-all and end-all for software projects. It's really closely tuned to how Pivotal works: XP with Lean trimmings in small teams with a product manager, designer and engineers.
The downside is that because it is deliberately limited, now and then you will find that you sorely miss something. Often those missing features are recreated with conventions around tagging or release markers. But tagging conventions are not the same as a first-class feature, for good or ill.
JIRA is massively more featuresome and flexible. These days it's grown into a workflow middleware which comes with a bug tracker as the first application installed. For some organisations that will make more sense.
Disclosure: I work for Pivotal, but not on Tracker.
