see more in the GitHub Flavored Markdown Spec
1 spaces
2 spaces
3 spaces
4 spaces (wrong) - rendering as code block
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More than three characters may be used spec source:
Spaces are allowed between the characters spec source:
Spaces are allowed between the characters spec source:
Spaces are allowed between the characters spec source:
Spaces are allowed at the end spec source:
no other characters may occur in the line:spec source:
_ _ _ _ a
a------
---a---