You don’t want to stop “Property Modified” from happening. If you do a “diff” of your tree and double-click on each file that is listed as “Property Modified”, you should see the details about the metadata properties that were changed. When you do a merge, the
mergeinfo property gets added to files and folders so that Subversion can keep track of which revisions were merged into which copy and at what time. Without this information, merging and viewing the history of branched/merged files would be extremely difficult.
Are the “Property Modified” files/folders showing changes to the
mergeinfo property, or something else?