No problem, I believe this is what you requested.
H2 Size In Preview, but Not Editor
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I have folding for headers enabled, but I'm unable to fold the text under this header in the editor.
H2 Size in Editor, but Not Preview
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I'm able to fold the text below this header which uses the three hyphens. It also renders the horizontal rule in the preview in addition to making the preceding line H2 in the editor.
H2 Size In Both, but No Horizontal Rule
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I'm able to fold the text below this header which also uses the three hyphens, but it does not render the horizontal rule in the preview. I don't know why. I didn't do anything different that I did in the above example.
When doing so I noticed that the forum renders them all correctly, except for the Obsidian specific editor functions (folding).