Board Thread:Support Requests - Getting Technical/@comment-25343201-20160113133802/@comment-24155515-20160113165638

I know how to merge the histories via delete/move/undelete (i.e.: you decide which article has the name (or the content) you want to keep, delete that article, move the other article to that article's name and then go to the delete log entry and undelete the edits that were deleted for the original page, then make sure that the revision showing is what you want to show on the page)... but while this seems to restore the comments to being extant pages, it doesn't seem to reattribute them to the page the same way a standard undeletion without the move on top would do, at least not according to this test I did--the only comment I can see on that page is the lone comment on the test article 2 that I made; the three for the linked page exist in my contributions (i.e. they *were* undeleted, but are just not visible on the article despite being comment subpages).

It might be best to ask staff for help; they probably have access to Special:MergeHistory, which may or may not be better at rescuing orphaned comments. At the very least, they may know better how to fix it.

EDIT: Actually, doing the manual history merging I described in the first paragraph did work; the comments for the undeleted article just didn't show until I made a new comment. So you could try that unless you'd like to be more careful and contact staff. (Also, I've deleted somewhat large pages and then had trouble with the ability to edit them when they were undeleted in the past, so if either page is large or has a lot of comments, it may be safer to contact staff.)

TL;DR: The first paragraph might do what you want, but you need to make sure you do it right. If you are at all worried about doing it wrong (or just otherwise want to play it safe), contact staff.