This is called context collapse:
Context collapse or "the flattening of multiple audiences into a single context"[1] is a term arising out of the study of human interaction on the internet, especially within social media.[2]Context collapse "generally occurs when a surfeit of different audiences occupy the same space, and a piece of information intended for one audience finds its way to another" with that new audience's reaction being uncharitable and highly negative for failing to understand the original context.[3]