In the Notes 8.5 Standard client, the twistie icons for section titles are almost invisible for certain section border styles (Gradient, Tab Diagonal, etc.).
In the Notes 6.5 client, the twisties were displayed to the left of the section title with the same color as the border color for the default style. For the Gradient and Tab Diagonal styles, the twisties were displayed with the same color as the section title text, contrasted by the border color as the background.
In the Notes 8.5 Standard client, the twisties are displayed in the same manner as Notes 6.5 for the default border style (displayed to the left of the section title with the same color as the border color). However, for the Gradient and Tab Diagonal styles, the twisties are displayed with the same color as the border color (not the text color, as in Notes 6.5). This makes the twistie icon invisible, with the the exception of a thin shadow line for 3D rendering.