Suppose you are writing a vim plugin hosted on Github (which seems to be a standard for now). You don't want to maintain two help files:
README.md (Markdown) and
doc/your_plugin.txt (vim help) with quite the same content but different markup language.
So it would be useful to have original help content in one place and automatically convert it to other. Or even better to have templates you can include in both places to have slightly different version of help to new user and search enginges (README.md) and active user (vim help).
How to make this templating or conversion?
UPD I've found another discussion: How do I generate Vim documentation from Markdown notes or inline comments, or are there better ways to add documentation?