There is some bad CSS in some of base templates that turns off word wrap when you add field help text to a form question.

The bad CSS looks like:

body.template-fg_base_view_p3 label.formQuestion {
white-space:nowrap;
}

The fix is to add to the local CSS this code:

body.template-fg_base_view_p3 label.formQuestion {
white-space:normal;
}

Solution by Peter Wood.