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BUG REPORT: "PRIVATE" MODULES

Modules tagged as "private" are visible to anyone. If the tag is not meant to mean "this is hidden from anyone but the module's creator", this should be made clear, otherwise that's a bug that should be fixed.

It is not a bug but an intended function. Private modules are just excluded from the module browser, but they are accessible if you know the URL. Same function exists on other sharing sites like YouTube too.
I see I failed miserable to make this clear and will improve the description text in the upload form.

The issue came up here: http://www.muffwiggler.com/forum/viewtopic.php?p=1747830#1747830

It's also not clear (at least to me) why "private" and "duplicate" are combined into one tag.

In the ModularGrid way the duplicate tag has the same purpose as the private tag.
They just should exclude modules from the module browser and search engine.
But you are still be able to add them to your racks if you like.
ModularGrid wasn't made on one day so a lot of inconsistencies from new features sneak into the system.
I try to iron them out over time, sorry for your inconvenience ...