The Settings->Repository details tab of each repository lists a setting:

Default branch

With a selector containing all branches. The comment for this field is:

Select the default branch for browsing the repository. By default, Git chooses "master".

This is correct, but misleading as this value actually changes the active brnach and thus impacts which branch is checked out when a user does a plain:

git clone <repo>

The comment (and perhaps the field name) need adjusted to make it clear this is more than just a UI setting, this has already caused one of our users to incorrectly change the setting not realising it impacted cloning of the repository company wide.