Non-directional chains are non-directional out of the box. However, the OP's question is clearly different. It is about non-directional chains that have already been installed and used for a while in one specific direction. They have been "broken in" in one specific direction, so to say.

The question is: what is the potential impact (if any) of reversing an "alrerady broken in" non-directional chain. This is a prefectly legitimate (and quite interesting) question. Those who do not find it interesting are not required to comment.