I believe I may have found a bug on the way the "Duplicate Files" option (on the main pane of Hazel) is implemented.
I'm trying to implement a ruleset which removes duplicated files from all subfolders of a given folder. I implemented a VERY simple ruleset; it has just one rule, that is the standard "Kind is Folder" + "Run rules on folder contents". In the base rule I set the "Duplicate Files" option.
When I run this ruleset on a single folder, it works perfectly, and it does delete all duplicate files. However, when I run the same ruleset on a folder with subfolders, duplicate files are not deleted. The folders are being all inspected (the logs show the rule descending into each subfolder) but the "Duplicate files" action is not applied on each subfolder.
This is a serious failure for an otherwise great product (which, by the way, I registered today, as I was very impressed with its power). However this bug may require me to resort to writing Python scripts which is something I though Hazel could help me avoid.
Hope you check into this and provide a workaround, or (better) fix it.