Yes, we'll have various other categories for historical periods eventually -- both for more individuals and for groups and themes.  Exactly how we'll do that is as yet undecided.  Proposals are welcome.

Rousseau is a tricky case -- born in Geneva, buried in the Pantheon!  He's often described as Swiss-French, and Encyclopedia Britannica says "Swiss-born French philosopher".  As we don't have a category for Swiss philosophers of the period (yet, at least), putting him with French philosophers seemed to make sense.

The weird a's don't show up in my machine, but if they show up in yours, you might mention this in the bug report forum.