Steps to reproduce:
1. Create a new custom style (ezplatform.yml):

ezpublish:
    system:
        default:
            fieldtypes:
                ezrichtext:
                    custom_styles: [inline]

ezrichtext:
    custom_styles:
        math_inline:
            inline: true
            template: AppBundle::field_type/ezrichtext/custom_tag:inline.html.twig

2. Apply custom style and then turn it off

The whitespace character "&nbsp" is created at the end of the tag, however, when someone is used to use the "space" key he will have double whitespace, which may throw him out of sync with writing a large portion of text.