This rule must (almost) never be broken, as this would negatively impact the continuity of the scene and cause a lack of interest or disorientation in the audience. The only time it may be broken is for effect, other wise it would confuse the viewers.
Below is an example of both how the 180 Degree is abided by and also broken for effect, this disorientation used in this scene helps to emphasise the confusing mindset of golem/smegal as he has a conversation argument with himself- conflicting personality.
Below is an example of both how the 180 Degree is abided by and also broken for effect, this disorientation used in this scene helps to emphasise the confusing mindset of golem/smegal as he has a conversation argument with himself- conflicting personality.