The description "sets the indentation character" combined with the default value of a space led me to believe that this was a way to set a preference for tabs/spaces and choose a number of spaces per indentation all at once. I've updated the description to try to make its true function clearer.
* Added note on rmtrailingws
This behavior was unexpected for me, so it's probably good to let other users know which option has precedence.
* Added details to help command
Initially I kept trying to use `help <command-name>` rather than `help commands`