xml tags in ksh translation

Sorry, yes it is html (I spotted the <code>xml:lang</code> tag and didn't look closer).

Both your link makes clear that:
a) That sort of mark-up is a suggested guideline and may not be fully supported.
b) That it only applies to MediaWiki.

In the current case adding such mark-up will simply write it out explicitly (since anything else would be unsafe in the xml document where it is used).

The message was updated to support a second parameter (instead of assuming this was gzip). The first parameter is the same as before. The documentation was updated at the same time but I've now [https://gerrit.wikimedia.org/r/#/c/277955 also added examples] to make things clearer.