Ian Wells
JIRA - why Never Delete
I recommend never deleting any issues in JIRA.
The reason is confidence in the system to act as a source of truth - I have found if staff notice one thing was deleted, that raises concern that other work they did may have been deleted and to not trust it - JIRA is really excellent as a source of truth because it contains a complete history of everything that has been done to a ticket, which builds trust among team members about what they did and what they asked for)