It's actually not em-dashes, they are en-dashes, which is either intentionally to deceive (e.g., swapped) or used incorrectly. Both of which are bad, it's up to everyone to decide on which is worse coming from MITality.

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jacobolus 5 hours ago | parent [-]

Spaced en dashes – like this – are a correct and accepted typographical choice. Whether to use spaced en dashes or (spaced or unspaced) em dashes is a matter of taste or local convention, and varies from one publication to another. Other than a typo or two where the space was left out on one side of a dash, the dashes in this linked document are just fine. See https://en.wikipedia.org/wiki/Dash#En_dash_versus_em_dash

	▲	phasefactor an hour ago \| parent [-]
		I was not claiming they are not correct punctuation/syntax. My claim is just no one uses them that frequently... When you see dozens of them in the first few pages of a document it raises suspicion.