This is an opinionated wiki implementation with wikitext as source.
Wikitext is a standard defined by what-ever mediawiki implements. As such, we implement only a subset of wikitext. The subset we implement is heavily opinionated and forces the wiki writer to be more consistent and more easily rejects broken syntax.
As example, setting both "none" and "left" on an image will return an error (although it does save).
This causes a "badge" on the top right indicating there is an error on this page.
Similar things happen when you try to set a caption twice, as example: