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I'd say yes if you're careful about it and don't overdo it. Different formatting can be useful in quickly alerting the reader that the text is from an article or an email, particularly if it begins...
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#4: Attribution notice removed
Source: https://writers.stackexchange.com/a/21611 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/
#3: Attribution notice added
Source: https://writers.stackexchange.com/a/21611 License name: CC BY-SA 3.0 License URL: https://creativecommons.org/licenses/by-sa/3.0/