User blog comment:Fimber/What exactly was "The Golden Age"? (Spoilers)/@comment-5674726-20121222000908

establishing the Round Table and marrying a servant girl

I don't think that we can give any Golden Age Brownie points for the latter.

Arthur married a woman he loved, just as Uther did. As a consequence of his choice, the opportunity to unite Camelot and Nemeth was lost, and the disputed lands were surrendered. Arthur is fortunate that Princess Mithian and her father apparently weren't ones to readily take offence. You'd think that most royals of the period would be find it more than a little insulting if they/their daughter was brought to another kingdom and announced as the future Queen, only to be rejected, and seen to be rejected, in favour of a servant. Guinevere's background does not appear to have had any affect on her actions as Queen; for somebody who wasn't familiar with the first four seasons, there's very little that would let them know that she wasn't of noble birth.

As for the knights, even if we assume that Arthur has abolished the prohibition against non-nobles serving as knights, instead of contenting himself with knighting four commoners (as far as he knew) on a whim, that has very little impact. Commoners who are sufficiently skilled in combat can hope for advancement but that's about it.