Hello, I'm currently testing parental control systems to see which adult content tagging systems they respect. With all the adult content filters enabled, this extension fails to block sites based on various meta tags used by adult websites to identify themselves as such.
I've tested the following meta tags in use by adult websites and none of them cause the page to be blocked:
<meta name="rating" content="adult" />
<meta name="rating" content="mature" />
<meta name="RATING" content="RTA-5042-1996-1400-1577-RTA" />
<meta name="rating" content="RTA-5042-1996-1400-1577-RTA" />

This lets me access 18+ twitter profiles which would otherwise be blocked.

Also, all adult sites I've checked so far include at least one of these tags, so I think it makes sense to check for them.