Check the screenshots:
video options: http://steamcommunity.com/sharedfiles/filedetails/?id=912554681
no weird triangle: http://steamcommunity.com/sharedfiles/filedetails/?id=912553485
weird triangle appears: http://steamcommunity.com/sharedfiles/filedetails/?id=912553866
Both screenshots are at the limit where it appears/disappear
video options: http://steamcommunity.com/sharedfiles/filedetails/?id=912554681
no weird triangle: http://steamcommunity.com/sharedfiles/filedetails/?id=912553485
weird triangle appears: http://steamcommunity.com/sharedfiles/filedetails/?id=912553866
Both screenshots are at the limit where it appears/disappear