Address discrepancies between markdown preview (when editing) and rendered result

Per @traxam, these issues are due to the editor using a different markdown engine than the rest of the site, but here's what I've noticed so far:

Nested bulleted list items using -

Looks fine in editor:

- one
  - a
  - b
- two
  - c
  - d

Looks like this in the result:

• one
• a
• b
• two
• c
• d

Workaround

* one
  * a
  * b
* two
  * c
  * d

Horizontal lines on blank line between header and content

Looks fine in editor:

# Header
---
Some content

Looks like this in the result:

# Header

Some content

Workaround

# Header

---
Some content