In AX 2012 R3 there was a case forwarded to me by a user who claimed that they posted a journal with a reversing entry but the reversing entry did not post.
At first I was certain this was not possible, but then I was able to understand what happened. When I checked the original journal I found that on the header level the check box was clicked however the lines did not have the checkbox ticked.
I was able to replicate the same, the user had first not setup the reversing fields on the header and instead had created the lines then had gone back to the journal header and had checked the reversing entry fields on the header. This of course would not effect any of the already existing lines and so the journal posted without the reversing entry since the lines did not have the “reversing entry” and “reversing date” entered.
Keep this in mind folks. I did a more detailed post on the reversing entry functionality in my earlier post here, please review the same for more details: