I don't know if something has changed on the Economist website, but for the last couple of weeks abbreviations like "DNA" and "FBI" are coming out as "dna" and "fbi" for me.
e.g. this is the case for:
https://www.economist.com/the-world-...05/26/politics
Looking at the page source, it seems they're using:
<small>dna</small>
and in the output file, it's rendering as:
<small class="calibre14">dna</small>