Note: In the meantime, I have added the workaround from T119702#2188976 to the template in question, so error messages from this specific template will not appear in TextExtracts anymore.

While I haven't actually looked into the extension, I assume that it works by simply prefixing all given selectors with #mw-content-text. This conflicts with the point "UI elements should not be style-able by this method" because #mw-content-text can indeed contain UI elements. This is T37247.

Just a guess: MediaWiki:Onlyifediting.js needs to be fixed for a recent change in the <charinsert> extension, see https://lists.wikimedia.org/pipermail/wikitech-ambassadors/2016-May/001417.html.

In T76234#1144524, @Mormegil wrote:

As is, <indicator> is just unusable and needs to always be manually wrapped on wiki into a <span> or something.

The negative feedback was, amongst others, here and there.

It would be really nice if software developers would think what they intend to do, and test whether their patches actually meet the intentions. Especially if it's something so easy to test as a background color. This is what happened so far:

In T134515#2334143, @Edokter wrote:

It applies to all skins.

In T134515#2313017, @gerritbot wrote:

Change 289549 merged by jenkins-bot:
Improve unstyled updatedmarker

https://gerrit.wikimedia.org/r/289549

In T483#2211010, @TheDJ wrote:

We have #mw-content-text that contains all generated output for wikitext pages, but more importantly the classes mw-content-ltr and mw-content-rtl.

For dewiki, this change would be somewhat problematic.

In T119702#2079664, @Robert-RtC3V wrote:

While this has not been fixed, is there any workaround?

TextExtracts should also ignore style=display:none

Thanks. So IMHO the only potential bug here is that the app does apparently not load MediaWiki:Mobile.css. I don't know if this is intended or not and will therefore leave the task open.

A subtemplate of de:Template:Coordinate was inserting garbage into the page. I have temporarily "fixed" it by hiding the garbage with inline CSS (style="display:none"). The proper fix needs to happen inside the template.

The problem comes from the German Wikipedia's Coordinate template. It inserts some "technical stuff" in geo microformat, but no inline CSS to hide it.