Tickets are for tracking bugs and enhancement requests. They are very simple. A title, body, and status. The opinion is that a ticket body should always have the definitive statement of the problem. If the problem changes, the ticket body is updated to reflect the most current understanding. This obviates the need to read through multiple comments to understand the issue that the ticket aims to address. Honestly, comments for tickets is a very bad idea.

Tickets are versioned. If a user deletes important information, delete the user (assuming she is being malicious) and restore the previous version. When a ticket is closed, update the body to reflect the resolution.

Tickets have several states: open, fixed, related, duplicate, invalid. Those should be self-explanatory. Tickets also have one author and one owner. A user can take a ticket to indicate that they are working on it. Anyone can modify a ticket, which includes updating the information, changing its status, etc.