When moving a forum topic to a different forum, leaving behind a shadow copy, number of comments in `forum_index` table is twice as much as it should be. The query counts the comments for the original node and for the shadow copy as different comments. It sums the comments counter for the original node and shadow copy and applies it to each node attached to a forum.
The situation is probably the same if there are multilingual nodes.
Can be reproduced on latest fresh Drupal installation, requires `advanced_forum` module to see wrong post counters. The query from `advanced_forum` uses `forum_index` table updated by `forum` module after any operation applied to a comment.
Needs work
1.0
forum.module
Not all content is available!
It's likely this issue predates Contrib.social: some issue and comment data are missing.
Forum is approved for removal. See #1898812: [policy] Deprecate forum module for removal in Drupal 11 →
This is now Postponed. The status is set according to two policies. The Remove a core extension and move it to a contributed project → and the Extensions approved for removal → policies.
It will be moved to the contributed extension → once the Drupal 11 branch is open.