Reply removal ran fixed-point loops: per page, every pass scanned all
replies and searched a growing Vec of removed annotations; across pages,
every pass re-read every page's /Annots. A chain listed deepest first
added one reply per pass, so the work was cubic on a page and quadratic
across pages.
Replies are now indexed by parent (/IRT, and /Parent for pop-ups across
pages) once and walked from the removed annotations with a HashSet, so
each link is followed once. What is removed is unchanged.
Dylan M. Taylor
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