command-line-parser

I know it's really an edge case since it can only happen when not reading the awesome documentation properly.

But since it's actually a contradiction according to the documentation and other similar things are also throwing an error, you might want to consider checking for this case and throwing an INVALID_DEFINITIONS error?

Alternatively it would make sense to just document which one wins,

I guess there is no real consistent scheme, but quite a few tools capitalize the help section headers.
So maybe a flag could be added to do the same when using kotlin-argparser.

So showiing

Usage: [-h] [-a] IMAGE-DIRECTORY MARKDOWN-FILES...

Optional arguments:
  -h, --help        show this help message and exit

  -a, --auto        Automatically remove orphan images


Position

Apparently GoDoc cannot show documentation for exported methods of un-exported structs, and it makes no sense to export parser and/or command, thus this project should provide its own documentation page.