Putting a spoiler on MathJax equations does not work well sometimes, as reported here (1st answer).

For example,

$$a=1$$ $$b=2$$ $$c=3$$

can be written using

> $$a=1$$
> $$b=2$$
> $$c=3$$

or

> $$a=1$$ $$b=2$$ $$c=3$$

However, writing

>! $$a=1$$ $$b=2$$ $$c=3$$

or

>! $$a=1$$
>! $$b=2$$
>! $$c=3$$

results in no line breaks in the preview pane. To see this in action, edit this post and look at this block:

$$a=1$$ $$b=2$$ $$c=3$$

Where have the line breaks gone?