If I type <nowiki into a Flow VE-mode text entry area, I get the "wikitext markup detected" message* at the top-right corner:

1. That message needs to be tweaked to suit Flow's use-case. It could say something like:

You are using the visual editor - wikitext does not work here. To switch to source editing at any time without losing your changes, click the </> button.

2. It also needs to be relocated, probably as a flyout menu similar to the anon-warning flyout. (Because the current top-right location means it is invisible, unless the user is scrolled right to the pagetop. Also because that would be more logical/usable.)

*VE's message is in the strings (mediawiki:visualeditor-wikitext-warning-title) and (mediawiki:visualeditor-wikitext-warning)

Bug initially reported at https://en.wikipedia.org/w/index.php?title=Topic:Slvvxa7d3qxjnwpt&fromnotif=1