Branch Mess occurs when contributors to the wiki are apprehensive about deleting existing content, so start to branch the content instead. Eventually too much deprecated information is stored in the wiki and it becomes difficult to locate the latest version.
Pages start to be labelled with qualifiers, e.g. an “Instructions” page becomes “Instructions (Old System)” and “Instructions (New System)”. An even worse scenario is when the pages aren't labelled to indicate which is the old system and which is the new system.
Remind the wiki contributors who are apprehensive about the “Remove” button that a page history is kept for all changes. Ask them to move forward instead of branching, and be more liberal with the removal of old content that is no longer relevant.