For plugin descriptions, you can embed you link in the description field of the plugin.json file using the standard HTML format:
"description": "<a href='https://google.fr'>This is a link</a>",
Unfortunately, the same option is not transposable to Prepare recipe comments. However, you can leverage Discussions inside of your Prepare recipe to further document it. Discussions can also be seen from the Flow's UI after selecting the Prepare recipe, and they are compatible with the various rich Markdown formatting options offered in other places like Wikis.