Birthsign-related Fortify effects don't affect skill training cap
Example: My character's base Personality Attribute value is 30, but my star sign (The Lady) fortifies +25 to this. I can't train my Mercantile skill above the Personality attribute, but it doesn't take into account the +25 constant fortification, so I cant get higher than 30 Mercantile until I upgrade it at a level up. AFAIK Vanilla allowed you to train up to fortified attribute's value.
(RM-1816 from redmine: created on 2014-08-16 by Thomas Callaghan, , relates #1751)