Minor improvements to the recalc explainer

[captainbrosset]

I made a few improvements to the style recalc explainer. Here is what I did and why:

1. Moved the feedback section all the way to the top so it's easier to spot.
2. Moved the cons about the tracing UI into the "existing solution" section. I think it belongs there.
3. Added \ characters to force line breaks in the rendered HTML (single line breaks in markdown do not create a <br> in html, if you want to a single line break (i.e. not a new paragraph), you need \). And did some other minor md fixes.
4. Added a red box around the checkbox in the screenshot.

[bwalderman]

LGTM, I just removed the \'s for single line breaks. I was asked to add line breaks in the raw markdown to make diffing changes easier but these aren't meant to be rendered.