User blog comment:DaNASCAT/Technical Update: August 19, 2014/@comment-452-20140819181031/@comment-1158325-20140825063114

You should have made the threshold more than one linked image, I'm now going through removing it from galleries where people added a useless link. Don't want regular galleries to be treated as some kind of navigation in the future.

I also found a bunch of "undefined" entries in galleries which nonetheless caused them to be marked as navigation. Guess that was part of some past (or god forbid, current) bug.

Also found a gallery full of "|link=" marked as navigation. Doesn't seem very navigate-y to me.