In spoiler tags bullet points will only change their visible state when the browser is scrolled up or down, with the arrow keys or the mouse scroll.
The bullet points will change their visible state to however visible the rest of the spoiler is at the time of scrolling. For instance, if you hover your cursor on the spoiler tag, the text will become visible but the bullet points will not, if at this point you scroll down one tick; suddenly the bullet points will become just as visible as the text in the spoiler. If you move your mouse so that the spoiler is not shown and then scroll the screen, the bullet points will disappear. If the text in the spoiler is part way between fully visible and fully hidden and the screen is scrolled, the bullet points will become partially visible and remain that way until the screen is scrolled again.
Note this is on chrome on windows 8.