In https://jira.atlassian.com/browse/BSERV-9254 (Allow "Delete source branch after merging" to be enabled by default), the default of this option was changed to enabled and there is no way to change the default. This means all users need to uncheck this box to avoid inadvertently deleting their source branch.

The suggestion is to add an admin toggle to allow the administrators to decide if the default for this should be on or off.

At this point, our company is holding off on upgrading past 7.2 to avoid consuming the BSERV-9254 "feature".