Glossary
Cross-exchange dedup
The rule that a post you have already engaged with is excluded from every other exchange, permanently.
Engage with a post in the comments exchange and it will never appear in your saves or shares queue either. The exclusion is per-post and per-queue, and it does not expire.
This is why an exchange can feel quiet for an established account: it has already seen a great deal of what is available, and the engine will not recycle it.
Follows are deduped permanently by nature — you can only follow someone once. Story views are deduped per calendar month, because a permanent pairwise block there would burn a useful pair after a single view.
See also