In French, AutoFormat automatically inserts non-breaking spaces before quotation marks, interrogation/exclamation marks and semicolons. It should also add them before percent signs (%): the rule in French is that punctuation marks constituted of at least two parts should be separated from the preceding text by a (non-breaking) space.
fixed for LibreOffice 3.5
The correction breaks the user interface : no space should be inserted before a % sign because every time you key in a percentage value, the space is added and the cell gets a string value instead of a numeric (percentage) value.
It makes entering percentage in a cell a terrible experience (must go back to edit the cell content and remove the space sign)
I've filed the problem you report as bug 54686.
(In reply to comment #4)
> I've filed the problem you report as bug 54686.
I close this, because a new bug was filed for the new problem.