Formatting problem with “invisible” comments

Question

I posted an answer and tried to make some of my hints invisible (but visible when you mouse-over them).

Formatting didn't quite work, and I split the comment into three lines making only the first and the third invisible, as follows.

If $K=1-\frac{K_1}{2K_2}$ then clearly $K<1$.

Let $\lambda=\frac1{2K_2}$ so $K=1-\lambda K_1$.

Then $0\le\frac12=1-\frac12=1-\lambda K_2\le1-\lambda F'(c)\leq1-\lambda K_1=K<1$.

If I try to make all three lines invisible, this is what I get (and it is obviously not what I want).

! If $K=1-\frac{K_1}{2K_2}$ then clearly $K<1$.

! Let $\lambda=\frac1{2K_2}$ so $K=1-\lambda K_1$.

! Then $0\le\frac12=1-\frac12=1-\lambda K_2\le1-\lambda F'(c)\leq1-\lambda K_1=K<1$.

Or if I combine all three into one, again I don't get the result I want:

! If $K=1-\frac{K_1}{2K_2}$ then clearly $K<1$. Let $\lambda=\frac1{2K_2}$ so $K=1-\lambda K_1$.
Then $0\le\frac12=1-\frac12=1-\lambda K_2\le1-\lambda F'(c)\leq1-\lambda K_1=K<1$.

There is either something that doesn't properly work as intended, or I do not understand the proper way to format. The answer where all this occurred (just in case you would end up voting :) is at https://math.stackexchange.com/q/3406622

Thank you for your help!

Answer 1

This seems to work. (Instead of <br> you can simply use two spaces, if you prefer.)

>! If $K=1-\frac{K_1}{2K_2}$ then clearly $K<1$.<br>
>! Let $\lambda=\frac1{2K_2}$ so $K=1-\lambda K_1$.<br>
>! Then $0\le\frac12=1-\frac12=1-\lambda K_2\le1-\lambda F'(c)\leq1-\lambda K_1=K<1$.<br> 

If $K=1-\frac{K_1}{2K_2}$ then clearly $K<1$.
Let $\lambda=\frac1{2K_2}$ so $K=1-\lambda K_1$.
Then $0\le\frac12=1-\frac12=1-\lambda K_2\le1-\lambda F'(c)\leq1-\lambda K_1=K<1$.

This was the suggestion from an older thread on meta: Multiline hidden text

You could also try some of the workarounds suggested in this question: Consecutive spoiler blocks (>!) are shown as blockquotes. (And in other related posts which are linked there.)