As long as you don’t click on the font name, font weight or font size, these attributes are not set. They will be used as defined in the paragraph style.
The difficulty comes from the UI ergonomy: font properties always show a selection but there is no visual difference between “inherited by default” and “explicitly selected”.
Consider for example the Emphasis built-in character style: it italicises the run of characters no matter the font. It is built without explicitly selecting a font face or size, only clicking in the italics variant.
In case you inadvertently clicked on a font face (or other attribute), you can revert to the “transparent” state with the
Standard button. This button has effect on all attributes of the current tab.
Note that the Default Style is not a real character style. Formally, you don’t derive other styles from it. Right-clicking on it and
New is the same as right-clicking in an empty area of the list and selecting
New. The resulting style is independent of any other.
To show the community your question has been answered, click the ✓ next to the correct answer, and “upvote” by clicking on the ^ arrow of any helpful answers. These are the mechanisms for communicating the quality of the Q&A on this site. Thanks!