Scenario:

When creating an issue the administrator may want to give the user the option to assign the issue to someone specific, so the 'assignee' field is added to the issue create screen. The default value of the assignee field is the current user, so this means that any issue created will be assigned to the current user by default. It should be possible to configure a default value for the assignee field so that the freedom to choose assignee is available, but if the user doesn't choose an assignee then it will default to automatic.

Documentation states:

Selecting a Default Assignee
You can optionally set a Default Assignee for a component. This will override the project's default assignee, for issues in that component. If an issue has multiple components, and the default assignees of components clash, the assignee will be set to the default assignee of the component that is first alphabetically.

Default Assignee Option	Description	Notes
Unassigned	The assignee of the issue will not be set on the creation of this issue.	This option will only be available if "Allow unassigned issues" is enabled in the General Configuration.

Which is not happening.

Workaround:

1. Set the assignee field manually.
   OR
2. Set a post-function on your workflow that overrides the assignee value the user sets. - the downside of this being that the user will be confused by the fact that they chose an assignee but it's ignored.
   OR
3. Remove the assignee field from the create issue screen so that it defaults to unassigned. - the downside being that you'll need to set up a new screen just for creating issues.