selecting a word, open context menù, the font list scroll to a max of 100 fonts, about a 3th of the total I have installed in my system.
In the icon bar all work as expected.
for history on this hard coded limit see:
[Reproducible] with "LibreOffice 3.5.2 - Windows Vista Home Premium (32bit) Spanish UI"
Already reported as 'Bug 34085 - [EDITING] [UI] List of fonts incomplete in context menu'.
*** This bug has been marked as a duplicate of bug 34085 ***