Maintenance of page - adding new languages

Indeed ;-)

The script catches both the template syntax and a user page link, but not a plain text name. (There are too many plain text remarks there)

Only languages having no translators listed would slip through, but are listed by the script for safety. There are only en, tokipona, and tw at the moment.

Good hint to ignore specific edits!

You should have yua on your list of supported languages with no translators - this is a new language (oops, I mean new to translatewiki.net!).

Seems neither in the list of supported languages nor having a translators subpage nor listed in this page, thus - no, it does not show up.
But it is in categories: Languages without translators, Languages, and Languages without Wikimedia projects.

Have just tried to find yua in the three categories Languages without translators, Languages and Languages without Wikimedia projects. For some reason these are listed under the letter 'U' instead of 'Y'!

Sounds like bugzilla stuff. It could be the intl category collation.

Reported on bugzilla 28736.

Some more small problems with the categorisation. Portal:Tw is not included in the category Languages without translators and this category is not listed at the bottom of the page. This language is supported although it has no translations nor any translators as yet. The portal Tokipona is also not included in the category Languages without translators but it is also not supported. I don't know enough about wiki syntax to know whether the reason for this is the way the template Portal is written, or whether it is another problem with category collation. I won't report this on bugzilla unless requested to do so by a staff member.

As of today the category Languages without translators contains 64 languages without translators which are supported by translatewiki.net, and it should contain one other language as explained above.