Previously, only edits to a closed question within the first five days pushed it back to the Reopen queue. That was the time frame after which on hold would change to closed.
The rules have changed now:
Currently, this means that a closed question will automatically be
added to the reopen queue when it is...
- ...Edited (body edits only) within 5 days of closure by the author. Or,
- ...Edited (body edits only) within 5 days of closure by a 3rd-party, provided the editor has not also flagged the question or voted to
delete it. Or,
- ...Sufficiently popular, where popularity is calculated based on question score, top answer score, or views per month. We're still
tweaking the exact thresholds for these, but right now they're fairly
generous - however, the most popular closed questions are being added
to the queue first.