Why HCU recovery is hard
The Helpful Content system applies a site-wide quality classifier — once a domain is flagged, every page on it is suppressed, even genuinely high-quality pages. Recovery requires the site-wide signal to flip, which means making site-wide changes substantial enough that the next core update reclassifies the domain.
Most attempted recoveries fail because they are too small. Tweaking title tags, adding author bylines, and refreshing a few paragraphs is rarely enough. The classifier was triggered by a pattern; reversing it requires changing the pattern at the level the classifier sees.