In my experience, it's a widely-followed convention. I use it frequently in an academic context.

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Cheers,
Paul Edstein
[Fmr MS MVP - Word]

In legal papers, it is the norm for signing dates, at least around here. I tend to spell them out rather than use superscripting.

Thank you all for the extra help and directions. As my way of giving back, I am sharing these to the younger staff in the office at the same time drumming into their heads that the computers are computers, not just electronic typewriters and storage devices.