FWIW, I managed to get something similar done today by accident. Using “create row” Shortcut with “Markdown” selected seems to sporadically create rows with bold formatting even in .txt files.
Similarly, if I run this script on a row in a .txt file, it will apply strikethrough formatting, even though formatting isn’t available via the standard cmd+k option. Outline-spacebar on the same row correctly gives me the “formatting not possible” warning.