I found a conflict with this mod and another very usefull and popular one:
https://vborg.vbsupport.ru/showthread.php?t=96602
This is the Prevent Double Post (Bump) hack and it seems Ajax are conflicting each other. When a member had a double post that should be merged to the previous one, the page must be reloaded to show up the merged post, the user had the feeling the board just blocked his post as screen remains the same and the user tried several times to post the same thing but when the page is reloaded there's a merged post full of the same edits.