Paragraph styles are not updated after a style modification directly in the text. On the contrary, the initial style is reactivated when the update option is activated (by clicking in the panel or in the "Style" menu, or with Ctrl+Shift+f11).
(The modification with the style editing menu works, only the update option has a problem)
Steps to Reproduce:
1. Apply a style to a paragraph (Heading 1, for example)
2. Change the appearance of the title (Font size, Bold)
3. Activate the style update
the initial style is reactivated
The new style should apply to all paragraphs of the same style (to all Headings 1 in the example)
User Profile Reset: No
I use Libreoffice for Debian.
I see this working, so NotABug, if in step 2. you change the appearance of the whole paragraph, as explained in Help.
Doesn't work for a part.
If I didn't understand, please set Unconfirmed.
Other possibility is to change this to enhancement, to enable updating styles from a selected part of a paragraph.
See also bug 76084.