thread merge

XenNulled submitted a new resource: - Fix built-in thread merge indexing/SERP issue, thread subscription deletion, add merge notice.

The built-in tool has 5 problems if you merge 'Thread B' into 'Thread A': 'Thread B' will only redirect to the first page of 'Thread A'. If 'Thread A' already had a full page of posts, old links will go to a page without the expected content. This can lead to compounding problems with Google...