Well that’s terribly confusing. So .anythingBut(“a”).then(“a”) matches “a”?? That’s so far off from what I’d expect that when I read the example for a URL:

(...).anythingBut(“ “).endOfLine()

I defaulted to assuming endOfLine mapped to [^\n]*\n and was left confused about the whole thing. I’ll take simple rigorously defined grammars over someone’s attempt to embed English onto them any day.