I see that hard links are applied to resource files in the album, as well as original images. This strikes me as being very dangerous. Imagine that you've installed a new version of a skin, and one of the resource files has been materially altered, but still has the same name. That resource file is then "magically" copied to all the existing albums that use that resource. But since the albums haven't been rebuilt with the new skin version, there could now be a serious, or even fatal, mismatch between the album page coding and the resource file in question. This is a prescription for trouble.

Perhaps this doesn't occur when one performs a true "install" of a new skin version, since that deletes the existing skin and replaces it. But if you manually replace files in the skin's resource directory, it certainly does happen.

On the plus side the feature has been available for a year now. Perhaps though the lack of any problem being reported is in part due to hard links being disabled by default.

Both when released, and in the manual, there is a warning about the potential for data loss when using hard links, though it only references the warning to using older versions of jAlbum on albums made with hard links enabled.

Does it need a one time warning pop up when enabling hard links?

What editor is it that rewrites the same file. The ones I've seen creates new files with the same name.
A skin can put a good amount of small res files in the target res folder, given that even small files can occupy far more data due to disk block sizes, I don't think the space saving is neglectable.

The question is just if this downside offsets the advantage of both saving disk space (remember disk blocks) and album build time... No other user has reported this as a problem and this feature has been available for over a year, right?