Emphasis, aka italics, with asterisks or underscores.
Strong emphasis, aka bold, with asterisks or underscores.
Combined emphasis with asterisks and underscores.
Alternatively, for H1 and H2, an underline-ish style:
- First ordered list item
- Another item
- Unordered sub-list.
- Actual numbers don't matter, just that it's a number
- Ordered sub-list
- And another item.
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