Nato (but VAT) has been preferred by the Guardian style guide [0] for a long time. I've never understood it.
[0] https://www.theguardian.com/guardian-observer-style-guide-a
The Guardian also does eg and ie, which, equally, I've never understood.
Re:Regarding the Em Dash
by cryptonector on Sunday January 07, 2018 @04:05PM
(#16092709)
As Churchill said, we're two cultures separated by a common language.
Full stops aren't generally used in abbreviations here, Mx Cryptonector.
Though there's a more recent trend to write "Nato" rather than NATO, which annoys me for the inconsistency that arises. Plenty of people pronounce VAT as one word, or PAYE, but these are usually left in capitals.