half link question

To answer your question on the cotter pin it is designed to be straightened and bent multiple time, however there will be a point where it will fatigue and fail so I would only install and uninstall it about 5 times before I would replace the cotter pin.

As far as a half link goes, with a master link or just drifting the pin you have to shorten or lengthen a chain by 2 links at a time because a chain has an inner row of links and outer row of links. You cannot just take one link out or in the case of the pin method you will be trying to align two inner or outer link sections and that won't work. Same with a master where you need to align 2 inner link sections. Remove one and you will now be trying to align an inner and outer link which won't work with a master. The half link allows you to go from an inner link directly to an outer link. Once you start playing with it you will see.