If you assign multiple character style to some characters, it'll work when you
do it on OOWriter (you'll see the characters with the combined properties of all
styles) but upon re-opening only one style will remain.

Steps to reproduce :
1/ Create a new document
2/ Type some text and select it
3/ Now bring the Style manager and go to character style, double click on one
(say Emphasis), your text will now be in italic. 
4/ Then shift-double-click another one (say Teletype) to add it. Your text will
now be both Emphasis (italic) and Teletype (Courier New).  
5/ Now save and close 
6/ Reopen you file. 

Actual Results :
  Italic (Emphasis) is gone.

Expected Results :
  Both character styles should remain.

Notes:
  The problem seem to occur on opening, because if you look at the XML the first
time you save, you'll see that text:span are correctly generated :

<text:p text:style-name="Standard">
  <text:span text:style-name="Emphasis">
    <text:span text:style-name="Teletype">Azerty</text:span>
  </text:span>
</text:p>

But after you open it, you'll see that all but one style remain, and accordingly
when you save the XML now looks like this :

<text:p text:style-name="Standard">
  <text:span text:style-name="Teletype">Azerty</text:span>
</text:p>


Regards,

Sylvain