During my research for "Bug 40700 - EDITING Writer Format Paintbrush formats more than selection" I found out that "Writer Guide - Word Processing with LibreOffice 3.3" can be improved in "Chapter 6 Introduction to Styles - Applying character styles".
It seems that a hint is missing how to transfer only character style without paragraph style: you have to press "Control" when you select the characters to what the style should be transferred using 'Format Paintbrush' (See Writer Help under heading "Copying Formatting With the Format Paintbrush").
I am not sure whether "Control" is valid for all OS.
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OK, I'll take custody of this on behalf of the docs team, and will forward this bug to the docs team mailing list to look for volunteers to fix the problem. If no-one steps forward in the near- to mid-future, I'll consider it's on my own to-do list with a number of other bugs to work on.
Help has been completed for 3.6.5 and 4.0.0, probably more early. So WFM