In this edit the user fixed a typo, but also there were three unwanted automatic transformations. Is there a way to prevent this?
Topic on VisualEditor/Feedback
Media link corruption is being addressed in Phabricator T198511.
The media issue is resolved. The second issue is caused by the non-standard "link" with transclusions. Visualeditor / parsoid doesn't deal with it correctly. That transformation is certainly an issue because any change to the document triggers it.
Great, the media issue is now indeed acceptable. I see however that it still replaces spaces by underscores in some cases.
Indeed. To answer the main question, the simplest way to prevent unintended transformations is to avoid using exotic wikitext markup. Transcluding part of a link is not only unusual but it is potentially confusing to new editors. In fact, I was under the impression that such transclusions should only work if prefixed by ":" , e.g.:
{{:Mediawiki:Example}}
Maybe the real issue is that perhaps second transformation should not work even with the current mediawiki parser. It may be an unintended side-effect because there could certainly be a template named "Template:Mediawiki:Example".
Although it doesn't discount the accuracy of your report. Visualeditor should certainly not be transforming things that the user didn't deliberately edit.
You are right, the link with Mediawiki:-transclusion should be substed; if and when the tracking category is renamed, its links are easy enough to find.