I did check the Spacecraft Thermal Control Handbook as well as the MLI guideline (PDF) document and you’re right they do mention goldized kapton as one of the materials used for MLI. But if it’s still used, it’s pretty rare - the standard MLI design uses aluminized polyimide. And I still think the above web site was written by someone who didn’t know, because it specifically says “gold-coated mylar” which is not even mentioned in these cites.
And the reason why gold was used on the astronauts’ visors is that it’s by far the cheapest metal, by area. That layer of gold is really, really thin, thinner than it would be possible to get a layer of any other metal.
That may be true for mechanically rolled metal film, but I think the visors had vacuum-deposited coatings. There are a variety of metals that can be vacuum-deposited in as thin a layer as you want.