Changing a font weight from 600 to normal

Well, that’s a first. My single biggest readability gripe on the web is when a site changes its default font-weight to 300 (i.e. makes it thin). I’ve just changed one from 600 to normal (i.e. from semi-bold). TBF, it didn’t look that bad, and I guess it’s only what iOS does in its Bold Text setting.