Hacker News Reader

You can just pop open a section of the zipper, then use the zipper over the opened chunk of zipper and it re-seals it

Ah, if it has two independent pull-tabs and they are locked together this works.

If you have one pull tab locked to the end of the zipper this does not.

Come to think of it some of my luggage also has locks that secure the zippers in place. Similar to this photo:

This would also hinder this method of opening a bag.

Open - probably not. Open and reseal and you are none the wiser - probably.