xml tags in ksh translation
So, it is HMTL, and not related to XML.
Yes, such tags were there. Italics are used to properly mark up words and abbreviation which are of another language and or may not be commonly understood by non technical users, see [1] and [2]
A problem here might be that the message has been reused with another parameter set, where each parameter itself is one of a choice of messages that should now have the markup, but the message documentation was only partially updated. I am going to check that and make sure, it only occurs once, once the message documentation has been updated so that I can know which messages are inserted as $1 and $2, respectively.
Sorry, yes it is html (I spotted the xml:lang 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 also added examples to make things clearer.