As a user, you can view your private tickets from your Client Portal. There is also support for public tickets to act as a Knowledge Base.
Try the Client Portal
This is the default way to allow users to view their submitted tickets and allow them to reply to them. Setting it up is very simple using the Client Portal shortcode. The relevant documentation can be found here.
To try out the Client Portal, click here.
Replying via email
Apart from using the Client Portal, the users can also reply to the email response they received directly from their email client; these replies will be imported as new messages to the existing ticket.
Public Tickets List
WPHelpDesk offers a way to use tickets as a public forum or a knowledge base. You can read more in this documentation page. The demo site will be updated with some examples in the future.