Ensure system level functionality does not interfere with in-game accessibility functionality. An example is system notifications appearing in the bottom-middle, where they obscure in-game subtitling/captioning.
Bottom/middle subtitle positioning is standard across industries, so the notifications need to be positioned somewhere else. Notifications appearing at the bottom-middle can sometimes be game-breaking even for players who don’t have subtitles turned on. For example, Telltale’s games, where notifications obscure conversation choices; choices that a player must read and choose from within a time window of just a few seconds.
Bottom-middle aside, the bottom corners usually have more critical information (i.e. information that needs to be referred to more often) in them than the rest of the screen, so top middle or top corners would be better.
Top-middle notifications on Xbox 360
Top-right notifications on PS4