This module's primary usage is on fieldable entity edit forms, which primarily exist in the Drupal admin UI and is intended to improve the admin experience for non-power users who depend on helper text to indicate best practices while they're working in context.
On summary text fields the font size doesn't match the description text for the summary field.
This contributes to an inconsistent look & feel which cheapens the admin experience.
In this example, we're using text_sumary_options with a configuration to always show the summary field from the body:
Detect (or expose) the classname to use from the admin theme to style the counter text like form field description text.
In this case the class form-item__description fixes the style.
Active
2.1
User interface
Thanks James for requesting this. I agree that doing so would improve the user experience. We'll discuss as maintainers the best way to implement this, but encourage anyone from the broader community to share their ideas (and even patches!) on this issue.