Well, I'm using Word for Windows, and undoubtedly there are differences between platforms and versions. Usually, though, you should be able to modify the paragraph formatting in a style without affecting its font formatting.

The same should apply to font formatting, italics in this case, applied on top of the style as direct formatting--it shouldn't be cleared unless you reapply the style (or explicitly reset the font formatting of course). When you reapply a style, font formatting applied to more than 50% of the paragraph will be lost.

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Stefan Blom
Microsoft Word MVP

Microsoft 365 apps for business
Windows 11 Professional