When a text mode was added within VE it violated expected behavior for text mode paste. It treated CTRL-V paste as formatted HTML, attempting to encode that formatting into wikitext. Community members unanimously described that behavior as a disruptive bug, saying the expected default paste behavior in text mode is a text paste. That unanimous feedback appears in T153315, it appears across various related phabricator tasks, and was posted in various on-wiki bug reports. The bug extended to Flow's text mode due to editor integration.
Task T190079 disregarded the unanimously expressed expected behavior. It created a disruptive popup when a paste is attempted. Paste is a common and fundamental aspect of text editing. The popup unexpectedly and disruptively obstructs the flow of editing every time paste is used.
The disruptive popup should be removed, and CTRL-V paste should be treated as a text paste when in text editing mode. The shortcut for alternate paste mode, CTRL-SHIFT-V, may be used for the alternate HTML-formatted-paste-encoded-into-Wikitext.
I expect resolving this task will involve a negligible quantity of code work, of almost trivial difficulty. T190079 would be rolled back, and it will probably be necessary to swap the behavior of CTRL-V and CTRL-SHIFT-V in text mode.