How to enable hyphenation of this word? The hyphenation points are already being considered. I put @loggingall in the source and inspected the resulting paragraph breaking; it has the expected discretionaries for the "determining".
What's happening is that TeX is trying to minimize badness over the entire paragraph, by making the interword spaces as equal as possible. In this case, the whole thing has to be set far too loosely, due to the vast unbreakable url. So the interword space huge. So the intersentence space after "Word_Boundaries.", which is 3x the interword space, becomes truly enormous. The last line has normal interword spacing because the hfil glue at the end of the paragraph overwhelms the stretchability between words. I don't see how anything can make this paragraph look decent except either allowing line breaks within the url or rewriting. Just a few more words before the url and it comes out ok. karl