When you reveal a spoiler the black rectangles go away and it then renders the text in white, but on a white background (light coloured theme) The text renders is exactly the same colour as the background and so you can not see it unless you highlight the post, this renders the background of the post as light grey and there is just about enough contrast difference to now read the text.
When spoiler text is revealed it should render in the same colour as normal text. I'm not sure why it's white.
See images below for demonstration.
It's an opinion piece and the thing about opinion pieces is that it can be totally stupid.
For what it's worth from a party unity perspective it would be better if he went now, the closer it gets to the election the more damage it does to the party when he neverably does leave. He should only stay if they are confident he can make it through to the election. It's no chance of that happening.
If he gets replaced then there is quite a lot of time still before the next election for his successor to fix things. If they wait until 18 months before the election there won't be.