HN does actually have automatic text filters to remove "extraneous" words from titles, even when they do fit. People have complained that the filters are too naive and sometimes destroy necessary context but for whatever reason the mods consider it necessary.
Could be one or the other, or both, but the filter's definitely there.
Fair warning HN also automatically replaces submitted links with canonical links despite most canoncial links pointing to the original domain for SEO purposes. There is no warning or feedback for any of this, you're just expected to notice and edit your post after the fact.
